Troubles Cumming

Does anyone struggle to cum during sex my boyfriend cums really fast and if he doesn't we go for a while and it gets I guess you'd call it raw cause it hurts after awhile and kind of burns we have no stis or anything like that but why is that? Most times he cums first and I have to ride forever to cum majority of the time I don't even, it usually takes him to eating me out to get me there can anyone relate or give some advice to improve this