Baby less than month

My baby will be there less than a month. My partner didn't treat me good the whole 9 months. He stays out all night and puts a code on his phone. We been together 6 years. We also have a 5 year old. I haven't been happy with the way he treat me now. I want to co parent. Just scared to do it with new baby. I'm thinking of leaving him before Jan 1st. He tells me all the time he want his cake and eat it to.. sometimes I'm really depressed. I just want to be happy and a good mom