Help!!

Luna❤️

So I had sex four days and he came on my back.. which I tried not to let it drip down to my vagina but now I’m kinda scared because I think I’m pregnant because a week ago before I left to Boston we did and the same thing happen, I’m suppose to get my period yesterday but it didn’t come my boobs hurt and nipples too and I have cramps but nothing. So I need someone to explain to me