Exercises I can do to build stamina/endurance?

Okay I know this is mildly embarassing, but I am pegging more often and always sore the next day. I want to build a work out I can do on off days or when we aren't seeing each other so I can perform better in bed and also just prevent my back from hurting after every time lol. The dynamic switch is obviously causing me to appreciate the amount of work men do during sex a little more.

What work outs can I do from home in order to be able to build my stamina and endurance to be able to peg him for longer or quicker or deeper/with more force? Would other toys be better? We aren't using anything particularly large atm. (5 inches and fairly thin since we are just starting)

I'm 5'2 and 120 lbs, and I have a disability in my arms so I cant lift more than 10lbs with my arms if it matters.