About 7-8 Weeks Ago I Had Protected Sex But 3-4

About 7-8 weeks ago I had protected sex but 3-4 days later I got my period that was heavy and lasted 5 days. I'm 15 and my periods have never really been regular and sometimes I skip a month but I haven't gotten my period in about 8 weeks. I don't have any pregnancy symptoms and I feel fine but my breasts do feel sore but not a lot just when I really grab them. This may seem like a stupid question I just worry a lot, is it possible I could be pregnant?