The Mistress Manual is a good book, by Mistress Lorelei or something like that, it's for sale on Lh, have a quick search. This might help you understand the mindset a little more?
I'm a sub by nature but have been discovering lately that I can actually switch, altho it's still a learning curve for me that I struggle with.
I try to reverse the thinking, as an example, a good 'friend' of mine is in the Army and I love sending him naughty texts at inappropriate times knowing it makes him squirm (in a good way), as a sub my thinking is that I am just sending him pics I know he likes, whereas as a domme, my thinking is I am teasing/torturing him making him hard when he can do nothing about it, so I am controlling his cock, not him, if that makes sense?
When I'm with a guy, I love receiving oral, in a sub mindset, I'm letting him do it cos he likes it, the fact I get pleasure is a bonus, whereas in a domme mind set, I am making him do it to me, because I like it and I don't care if he does or not, cos it's about what I need not him, the act is the same, the language can vary, but it's the mind that controls it...
As has been said, ask him what he means, it can mean something so very different to everyone. A guy I knew wanted the full works, the dressing up, the verbal abuse, doing exactly as I told him etc, another guy I know is on the more femme end of being a male sub and wasn't interested in any bondage type stuff, he likes being verbally humiliated, so he tells me... There is such a spectrum and far better to explore tentatively together than to assume what he wants.
It will take time, and you will have many internal wranglings but is possible to turn it on every now and then once you remove the pressure to perform, so to speak...
Good luck