Sex Help!?

I’ll be 26 and have been having sex for over a year and a half (first had sex at the start of 25). Had 2 partners after that first partner that I lost my virginity to(break up that ended up in me fooling with guys within a year 🙈) My boyfriend now is my 4th partner and has been bigger than the rest and has had much more partners and experience sex since a younger age. Our first handful of times having sex involved quite the amount of bleeding and now none at all. I have never been flexible and my boyfriend tells me I have tight hips ( he was a massage therapist for 5 years) and I should probably do some stretching/yoga to help. I have tried a bit and we have noticed me being a bit more flexible but being on top is still a task! I am not the thinnest, but I have been on keto for almost 2 months in a couple weeks and have lost 25lbs since we’ve first started being sexual. I have always been uncomfortable with my body but have been getting on top more (have never had different sex positions besides missionary) but I feel like my inability to be flexible and lack of sex experience makes the sex bleh. Tonight we had sex and granted my boyfriend was already asleep when I approached him for sex. He couldn’t get fully hard so he finished himself after we tried me being on top twice. He noticed my attitude change and we talked. I let him know that I thought it was just weird that he would rather finish himself (there have been other times he has when it was just me giving him a bj). He assured me that it wasn’t me. Flat out told me “ yes babe sometimes we’re gonna have good sex and sometimes bad. Our sex has improved, can it be better?, yes and I hope so... 🙄” He mentioned that if I wanted to improve then maybe looking up stuff. Soooo I’m here for tips? Suggestions? Exercises/Stretches? Positions? Tips on riding on top? How can I open/widen hips? I just wanna orgasm 😭😂