low abdoman on left side has been hurting since I last had unprotected sex

I had unprotected sex wirh my boyfriend but he pulled out. I understand that he could have pre ejaculated, and I wanted to know if it is possible that I'm pregnant. we had sex five days ago and I've been having a pain on my lower abdoman on the left side. it goes into my back and hurts when I press on it, like a bruise. I don't think its an ovarian cist because I would have felt discomfort during sex and this wouldn't be the first time and it isn't a blatter infection. I'm just really scared and I'm still in high school and I just don't know what to do..