Advice please

Hey, I’ve never made a post before but I was wondering if anyone could offer me some advice

So I’m 21 and I’m having trouble with certain positions whilst having sex with my boyfriend and it’s really affecting my self confidence especially during sex. In some position but not most it hurts slightly and it’s hard for him to enjoy it and cum as we have to change positions and sometimes go slow as I Cum first most times. Could anyone give me any tips on how to maybe relax more or become less tense as this may be the reason? Or is it something I’m doing wrong etc

Also could anyone give me any tips on how to perform better overall, especially when I’m on top as I’m really petite to my boyfriend and find it difficult to go fast when I’m riding him and wondered if there’s anything to help quicken my pace a bit more?

Thanks in advance x