I have a similar thing with my GF. Out of countless women/hetero relationships before her, I found the woman capable of surrendering my trust too.
We engage in a bit more than you do, which is to be expected since you stated you’re new at this, but realistically speaking so are we.
Like you/your partner, I’m not into degradation/humiliation.
I’ve always been the dominant one in every relationship/encounter before her.
But, she was in an abusive marriage for 20+ years and I told her before we were even an item there was nothing she could do to me to make me question my sexuality.
She told me before we were an item that she “had no voice, no choice, and no control.”
I told her I would willingly give her “control/dominance,” but she’s such an innate submissive woman it’s hard for her to do even though she loves it.
Having said all that, especially when it comes to pegging play or other such “vulnerable states,” as a dominant (pleasing fetishist); I still struggle both with wanting her to take control, and letting her take it.
The best way I can describe our relationship is that I’ve taken on the role of a switch/verse, but with women (her) only.
It sounds to me that you may find yourself in future similar situation. I mean this not with regard to anything that makes you uncomfortable (just to be clear, I don’t want to assume/offend, I just recognize some similarities from your post).
I think what has helped me the most is realizing (for myself, and her at least); it’s the power exchange dynamic, and her pure enjoyment when it happens that turns me on the most.
If you find any of this resonates, I have a few words of advice it’s taken me a long (going on 3 years, with mostly infrequent occurrence) of time to realize.
- Communicate. (Draw clear lines of what you’re comfortable with and what you aren’t) - and realize the longer you go the more likely those lines will change (for both of you), especially if you’re really wanting to take a submissive role that focuses on pleasing her. And even more so if she finds she really likes being able to be dominant when you choose to allow her to be.
(I said the “when you choose to allow her to be dominant,” part due to the hardships I have with trying to teach a purely submissive person how to be dominant, (even when she wants to be she struggles with this, and I’ve found this alleviated a lot of her anxiety in my situation. I don’t presume to know yours. 
)
This ensures you’re both on the same page and both of your expectations are met and mutual; and that both of you feel respected, heard and understood. As in, it relives a lot of anxiety in my experience.
And according to the copious amounts of research I’ve done with regard to this topic.
- Realize (and if you feel it is appropriate), verbally acknowledge that you understand she may be as nervous to mention something she’s interested in doing to you as you are mentioning it to her.)
In so doing you’ve made a “mutual ground of comfort” for discussions about future ideas/desires etc and trust me when I say this. Almost all women appreciate hearing the acknowledgment of how they may feel, but definitely almost all women love that you’ve simply taken the time to think about how they think or may feel about anything. This is especially true of something as tentative as this conversation can be.
Avoid flat no answers if she suggests something you’re uncomfortable with during this communication. I’ve found that answers to (flat no, internally) ideas are best met with answers more along this line of response. “I’m not sure I’m comfortable with that yet but we can look into that later on down the road,” and or however you would convey that in your own words.
- Be willing and capable of exploring your own boundaries of comfort. From Prostate play to Anal to Urethral to Bondage and or any other “kink” play (in which you would find yourself in a “non dominant position;”; I’ve found if I was uncomfortable with something initially, that exploring those limits of comfort by myself first have had amazing benefits for me when I tried them by myself when I knew I was in control.
This has allowed me to understand what I was feeling. Know the “that’s not supposed to feel that way if that’s going how it should,” and also “yay that’s exactly how it should feel when she does it to me.”
By amazing benefits for me, I’m not just referring to “in an us way.” I (without being too gratuitous), mean multiple orgasms with little to no thought, no refractory period, and so on.
Perhaps most interestingly, I’ve learned that for every “body part,” I’ve had no experience with for myself, but have knowledge of as a dominant pleaser that I began to explore for myself?
Has “unlocked” my bodies ability to enjoy other areas even with no stimulation to those areas.
(This is essentially referred to as forming new neuronal pathways to your brain to induce pleasure. If you’re at all curious about this you would be doing yourself and your partner a favor by doing much deeper research into this.)
(I would advise you to have clear communication about this if you choose to explore something “You’re not comfortable with yet but maybe later in down the road,” topics.)
I find that when it’s openly known?
There’s no guilt and no hiding or shame or fear of being “caught.”
She will mostly likely appreciate the fact you’re trying something she wants to do with you until you’re comfortable with her doing it to you.
And if you’re lucky, like I am, she will enjoy “catching you,” or “peeping/watching you.” And if you’re not, she will still appreciate that you’re trying something new to please her.
That last part of that last sentence. Is the definition of role reversal to me. As a man, even as a pleaser fetishist in a dominant fashion, I’ve always asked women to trust me, to explore their bodies with them (and of course had safe words if they had had “too much” pleasure and truly needed me to stop.)
But it was always about proving to them that what they thought was true of their bodies, (I can’t have more than one orgasm, I can’t cum without clitoral stimulation, I can’t squirt, etc). Was only true because they believed it and had no one try that had taken the time to make them comfortable, who had done the research/had the experience, to allow that to happen for them.
Well. If that’s how I’ve asked women to engage in activities with me. I’ve always felt it would be hypocritical to not do the same for myself, (to not have preconceived ideas, to not be willing to research and try something new, etc for her. To not trust her to treat me with the same respect and care I’ve treated all of them before her, and her with.
If that makes sense to you, about the role reversal. It’ll make exploring your own boundaries (for her), much easier to accept.
That’s the part that took me the longest to wrap my head around when I was uncomfortable.
Well. That, And buying toys (for myself, but really for her to use on me when I had become comfortable.) Because I’ve spent thousands on women but never anything on myself when it came to this topic.
Lastly, If you find it appropriate set some ground rules along the lines of “what happens in the bedroom stays in the bedroom,” when it comes to “role reversal.” That’s the only problem I’ve really run into, was my GF acting dominant in public when she’s not naturally dominant and I’m not naturally submissive. It caused some initial frustration/resentment until we navigated that hurdle.
I hope some of this was helpful to you.
And I hope you heard it with the intent with which it was spoken.
As advice but not implication, of anything you “should do or be comfortable with.”
No one has the right to tell you that. Unless you really fall down the rabbit hole and become her sex slave. And there’s nothing wrong with that either. If that’s what you both choose to do.
Best wishes down a very fun road to enlightenment, and I think you will find your relationship will blossom as a result of your willingness to “be vulnerable for her.”
Because, I assure you my GF appreciated it when I “switched,” and let her see I was willing to take the time to think how she felt, did what she does, and experienced what she’s experienced.
And she appreciates knowing when I switch back to usual, she’s still going to have the same man she fell in love with.
Let us know how your journey goes and kudos to you on taking the road less travelled.
I hope some of this was relevant and or helpful to your situation.
do I send her a thank you card?