I can't ride

my fiance wanted me to ride him tonight so I tried in multiple different positions and it works the best when he's sitting in a chair, anyway, I can only do it for a couple minutes because it feels like I'm doing constant squats and its so tiring and hurts and I've been doing it for over a year but like a couple times every few months so not a lot. I feel like I really disappoint him because he's seen all these videos in the past of people riding and having no problem (he was a porn addict but he isn't now and it kinda pisses me off when I can't ride because I can't match up to what he used to watch.) and he thinks I should be able to do that too now.