Could I really be pregnant? PLEASE HELP!?

I'm 15 1/2, My boyfriend is almost 18, we've been together for 1 1/2 now and have been having sex since december 2010. We use condoms sometimes but not that much, and I just went on vacation but right before we had sex for probably 10min (Quickie:P) in his car 2 nights in a row without a condom, but he did pee before and thats said to kill semen until you come again, and he pulled out like 2min before he came. People say that traveling can make your period late, and also stress, which there was a LOT of stress on that vacation, my entire family was there, not to include the most annoying cousins on the planet. I was getting terribly moody on the trip, but not so much on the way home. I've been feeling a little quesy at times but never really throwing up and my period is 2 or 4 days late (Cant remember exactly when my last ended but I think it did May 24, and a little tiny bit of blood for the next 2 days then completely stopped) I've also been feeling kind of crampy and burning "down there" and a little bit more c** coming out but everything else is pretty much normal. So could I be pregnant, or am I just late from traveling and stress?