PLEASE HELP ME

I'm 15. So me and my boyfriend had sex about a month ago without protection...  It was only precum but I normally have a really strong flow on my period for about 5 days. I got my period last week and it lasted 3 days and there was barely any blood. The past two weeks I've had really bad headaches and I feel sick a lot. I don't know if it's from stress or if I am pregnant.