I might be pregnant

Hello everyone

Soooo I need help. My boyfriend and I had sex 4 days ago and he ejaculated inside of me. My best friends birthday is tomorrow night and of course I want to drink and smoke some bud! I haven’t since we had sex because I’m scared but I really want to tomorrow ! My question is should I not or can I?? I don’t want to harm the baby but there might not even be one!! Also when can I start taking a pregnancy test? I usually get my period around the 22 of every month. Please help !! 😔😔 is it safe to do whatever I want until I get or not get my next period ?