AF . IS WEIRD idk what to think

Sooo my last af started Oct 21 ended the 25. And according to glow I was fertile on the 10 in which I did the deed also af came today I guess it af but its REALLLLY LIGHT like nothing is there. Ever since I was 13 my 1st day of EVERY period was heavy and painful and this one isn't. I've been having tender nipples and have been nauseous . Could I b pregnant is something wrong. To me this isn't a normal period AT ALL. especially since its 4 days late