If you are nervous about sex, sometimes your vaginal muscles tense up and make sex impossible, difficult or painful... It might be that, it does take some time to get used to also.
I've heard that taking a warm bath, taking ibuprofen an hour before sex, lots of foreplay first, LOTS OF LUBE more than your body produces, can all help... Also, ************ on your own, using a *****, and stuff that makes you feel more comfortable with sex can help.
It it hurts because it is going in deep, then he could be hitting your cervix, it doesn't sound like that, because you said he went slow, but it's worth mentioning. Perhaps he is too big and you can't fit all of it, it may be able to take more in the future.
It also may help if you are on top, so you can control how deep it goes in and what might feel good, or not painful.
I was very, very tight at first and had similar issues. Of course, I was with a dude that had a big d*ck, which was unlucky because I was so tight, it hurt like crazy at first. But it got better and better as I kept having sex.
It was painful five times? Go see a doctor.
If you are small, it may just take time and stretching. That is, if you are sure you're going slow enough to loosen up first, as it were. Use lube?
It is possible that nothing is wrong. It took a few times for sex not to be painful for me- probably 4-5 times. Also, try to relax as much as possible. If you tense up, your muscles tighten which can complicate things if you barely have it in.
size matters of your bf and your opening so may take a few more times till u start enjoying it