Uhhh. so last nite i was out with the boys from my job drinkin?

and, got trashed. ended up having with one of them :( problem? he's got a girlfriend and she's 5 months prego. i feel terrible. i also hope he doesn't say nothing to the other guys i work with. any advice? should i tell him it was a mistake? i'm sorry n to please not say anything? i feel like crap.... i don't do stuff like that. and he initiated it.