I might be pregnant

Hello everyone!

Sooo I need your help. My boyfriend and I had sex and he ejaculated inside of me 4 days ago. My bests friend birthday party is tomorrow and I really want to have a good time and drink + smoke weeed. I have done smoked or drink since he ejaculated inside of me because I am scared it might harm a baby that might not even be there but what if I am pregnant? What should i do? Should I do whatever I want until I’m officially pregnant or should I just cut cold turkey until my period comes? I get my period on the 22 of every month and that’s kinda far from today so I’m not sure what to do!! Any one knows or have been through the same ?