Have Had Irregular Periods. Was Sexually Active. No Periods And Have Fibrocystic Breast. Pregnant?

I am a 15 year old girl. I have had had my period since I was 12, and it is still irregular. I have been sexually active lately also with my boyfriend. We have used protection every time. I was supposed to get my period Saturday, July 6th, 2013, the last day I was sexually active. We used protection too. But a couple hours later, we were alone. He made sure there wasn't any precum and wiped any of it off if there was. I believe there was still some on the head though, and he stuck just the tip in, nothing else, and pulled out. I am not on birth control either. Well, I haven't gotten my period yet, and it is now July 8th. But my period is irregular. Sometimes I will even go months without getting it. My breasts are sore, but I believe that is because I have fibrocystic breast. It runs in my family. So, my question is, is there a possibility that I could be pregnant? There is no way I'd be able to buy a pregnancy test or anything to make sure. And I apologize for this being so detailed. Please respond as soon as you can. Thank you.