I'm fifteen years old I lost my virginity to my boyfriend of over a year who's 17 years old about two weeks ago. It bled a little the first time, then the next night we had sex again, and it bled a little again. I figured it was okay because I read on here it may bleed the first few times. About a week later, we had sex again. And again, it bled. But it bled more than either of the other times. Being the third time, and there being a little more blood, I started to worry. (it only bled while we were having sex, it stopped after) the first two times we had sex he didn't move much, same with the second time, but the third time hurt as much as the first, and he was a lot more into it, and doing it a little harder. Is it something I should worry about? I don't know what to do, or what's causing it.

Stop having sex until you are married.

XenoSapien

While I agree that you should wait that time has already passed.

A few things could be going on -
1) You said he was thrusting harder the third time - that can cause bleeding. Your vaginal tissue is delicate and can be torn and it will cause bleeding. As long as its not like your period its okay.
2) You could not be properly lubricated thus causing tearing.

Since my thought is that is tearing I'd give it a break for a week - EVERYTHING a break for a week. Tell your boyfriend your vagina is off limits in every way shape or form. You need to heal or you risk getting a really bad tear or an infection.

I also hope you are being safe and using protection.