Low key confused

Okay so me and my SO have been having sex for about a year. His penis is not huge by any means I would say it’s about average. I still have pain when we have sex. He will have both my legs up, one leg up, or doggy style even sometimes and I hurt. Some days I don’t hurt. There’s no particular pattern that I can see about the days I do hurt and don’t hurt. Sometimes when I don’t hurt I feel like I’m gonna pee... in certain positions I am not sure why this is... I am just confused idk what’s happening to me.