Need advice please /:?

I was supposed to start my period on the The day me and my bf had . The condom came off and got stuck in me and all his **** went everywhere inside me. Now im not on any bc cuz i take medication so i cnt. And i havent started. Im nvr late. Ever. The whole 6 yrs ive had it. Ive never been late. Im only 3 days late tt idk im never late. Nowwww any answers as to why have i not started? Dnt tell me i cud be pregnant. Can it even happen that fast? Or am i juss being paranoid?