pregnant? had sex, a week late for period, had an 8 day period; now I'm late.

hi, I'm a teenager and scared I may be pregnant. I had unprotected sex the first week of January, i didnt want him to finish so he didn't ejaculate at all (except maybe precum), anyways, I was a week late then finally got my period, I think. it was very heavy and I bled for 8 days. I've been having pain in my lower abdomen ever since though. now I'm two days late for my period in Febuary. what are the chances of me being pregnant? is it all in my head? please help.