Making sex feel better

I'm 17 and I lost my virginity last year to a guy who was also a virgin, I had to stop due to being uncomfortable even though there was no blood or sharp pain. I only had sex with this partner twice.

I have a new boyfriend and we haven't had too much sex but when we do I feel like I'm still a little uncomfortable and I'm really difficult to bring to orgasm, either by penetration or oral, which I blame on my crazy masturbation habits.

What are some tips to be able to enjoy sex more and be more comfortable? I also get really anxious right before and during, so tips on relaxation might help too