Can someone help? Am i pregnant?

Hi, i started my period on the day i was supposed to, it was decently heavy as the day went on i used a pad for two nights and i bled in them a decent amount. and then yesterday and today it has been super light. is it possible to be pregnant, because it’s only 3 days in. I’m on birth control also. Can someone let me know please! also my period last only around 4 days