Confused

Okay, so I got my menstruatal on January 5th but on January 16th and January 18th I had sexual intercourse ( one time was unprotected and the other time was protected ) Im positive that my partner had pulled out way before he came so no semen came inside of me but my stomach is feeling weird. Like i don't have any symptoms of pregnancy but i have a weird feeling and i have to do the number 2 in the bathroom very often. Could this be pregnancy, stomach virus or my period again? It's my lower stomach that is hurting.