I Had Unprotected Sex With My Boyfriend About 2 Days

I had unprotected sex with my boyfriend about 2 days before my period. My period seemed normal but it was blackish for like 4 days after it now I've been super tired and have had some off and on diarrhea. I normally go to bed at about 11 o clock but lately I've been going to bed at 8 ish and waking up at 6 and I still fall asleep in classes. Is there any possible way I could be pregnant? I don't think I am cuz I don't eat very much at all because I'm so busy with school and homework I just forget to eat and the baby wouldn't even survive would it?? Please help!!