Hey so i really love the idea Mrs kinky taking total control if me and using me as her little play slut dress me however she likes, treat me however she likes the rougher the better,
We have a strap on that we use from time to time, i have a few others anal toys prostate massagers etc, i enjoy a little anal but struggle with deeper penetration,it just feels more uncomfortable,
is there anyway to get past this?
i want her to be able fuck my ass as hard as she likes
Possibly a smaller strap on??? 
If it feels uncomfortable I wouldn’t push it. Discomfort is often a warning sign and meant to discourage rather than encourage - much like pain. I know many enjoy certain activities that result in both discomfort and/or a certain level of pain, but it’s always important to know and understand your limits.
Does ‘hard’ always need to also mean ‘deep’ ? Aiming for shallower penetration may mean she can thrust both faster and with more force without you experiencing discomfort and since there are more nerve endings around the anus than deeper inside may mean it’s also more enjoyable for you too.
Prep more beforehand with smaller toys that become more incremental. You don’t just suddenly change your anatomy to suddenly lose the bend at the end of the colon and get into deeper territory.
Practice and plenty of lube will help but go easy and work up to it slowly.
Our go-to dildo for pegging is an 8" Lifelike Lover dildo and, after practice, I can now take the full length.
I found that using a colon snake prior helped in our case. No issues whatsoever after warming up with it. 
As @rockstar says slow and steady start small and work up
This is the one we use.
Lifelike Lover Ultra Realistic Suction Cup Dildo 8 Inch - Lovehoney UK
It starts off with a small circumference so insertion is easy then the girth gradually increases along it’s length so it’s ideal for training.
Yes, like others have said, start small, take your time, dont rush it and build up to a bigger toy over time. If Mrs K wants to go hell for leather now then use something smallish like this , it will not take anything away her feeling of total dominance but make sure your OK.
Practice makes perfect! Start smaller and work up in size and length. Maybe consider buying an inflatable dildo that you can control the comfort size of.
I get pegged by the 10" Lifelike Lover dildo and the whole lot goes in although, to be honest, there is very little sensation past the first 6" or so. I dont think there are many nerve endings deeper in the anal oassage.