It burns down there?

So im 18 years old & I've been with my boyfriend for 5 years & we have never had intercourse without a condom; we always use one. So the other day we had sex & about 30 minutes into it, it started to feel like it was burning down there as he continued & it got so painful we had to just stop. I don't know why it's burning or what is happening but it kind of scared me. I have never had this problem before. So I'm not sure what to think of it. I'm not concerned of any type of sexually transmitted disease because we never do it without a condom! So what do you guys think it might be? Any feedback will be greatly appreciated, thanks!