help me please!!!

My husband and I have been married for 7 months going on 8. We are currently expecting our first child together and I'm looking to file for divorce. I feel like a failure as a mother already having to split up my family. He's been cheating on me our whole entire marriage 😢 me trying to make it work every time I've found out. Even when I ended up getting the clap. Yes I know it's very dumb of me to have stayed even after that so please don't bash me I already feel and look dumb as it is in this situation. I caught him again and his is the last damn straw I can't keep doing this to myself and I can't let my little girl grow up thinking it's ok for a man to do that to a women when he's supposed to love her. He's in the marines and he's the only one with a job at the moment. I want to file for divorce but I don't know where to start 😭 we got married and live Cali. I'm so heart broken to have to do this. I even found out he was with another girl who is pregnant and kept wanting to touch her belly when he barely even does that with our own baby 😭 what's worse is I'm stuck in PA right now with him and his family till the 1st. I have to pretend like everything is ok and I just feel so broken. I chose to have a baby with this man and now it's going to break her heart even before she's born with this situation. Is there someone on base I can talk to about filing for divorce and how does custody etc work if our little one isn't born till march?