I wanna birthday someone really bad tonight

My bf and I recently just broke up,it’s not even up to 2 weeks…This bastard and I are supposed to see tonight and I don’t know what made me go to the ATM to withdraw and voila,I see him with another woman inside his car who he claimed was his friend….am I wrong to think that even while we were dating,he was sleeping with someone else…..am still going to sleep over at his place but it’s gonna be ry messssyyyyyyy