I feel trapped. Advice please :(

I’m stuck in a terrible relationship. I’m 20, married, and have a one year old. Throughout my relationship my husband has cheated on me several times (including when we were dating). Not all sex related but flirting and sending pictures as well. He cheated on me when I was 9 months pregnant and we separated when our daughter was 3 months old. After about a month we talked things out and got back together. He didn’t cheat on me again for that entire year, spent time improving himself, etc. He has bipolar and flips his moods so he gets angry about stupid stuff and yells at me. But then other times he’s fun and loving. But I recently found on his tiktok him flirting with a girl and trying to FaceTime her and whatnot. I’m at my wits end with him but I have no money saved up, no car, and I could only go back to my parents temporarily because there’s already so many people there and they aren’t clean like they should be for a toddler to be there. My best friend has her apartment lease ending in September and would take me on then but idk what to do. Should I stay until then? I feel like I can’t really talk to anyone about it.