I need help

Soo for the passed few weeks my fiancé has been going out once or twice a week with a buddy that I DO NOT LIKE. And getting wasted and either not coming home or will come home at 2am. I am 16w tomorrow. I cannot keep stressing about if he’s going to come home that night, or not come home at all and then lose his job. Or what if this doesn’t stop and he does this when the baby gets here?!! I can’t handle this! We have been together since we were 15yrs old. And we are now 20. I need some advice from y’all!