Okay so long post sorry in advance. I just need some advice!!

My boyfriend and I started seeing each other Nov 1st. I have two kids from a previous relationship and am currently 26 weeks pregnant. He doesn’t have any kids. But was fully aware of the fact that I was about to have three and said he was fine with it. We fell head over heels in love, even talked about marriage. My one year old started calling I’m dad and everything. Well fast forward to Christmas. Me and my two toddlers stayed with him and his mom for Christmas and we had a wonderful holiday. He took me home on the 27th. On the 29th he texted me and said he felt financially strapped and he was stressed out and it would be best if we broke it off. Well me being completely in love with him of course I wanted to talk it out and work through it. He 100% ghosted me. I still talked to his mom and she kept me in the loop as to how he was and such. Well fast forward to Jan 18th. His mom called me and asked me who the guy was liking all of my posts on facebook( it was just a friend that I had been talking to and crying to about my frustration) and then she goes on to tell me that my ex had his ex at his house. Of course I BALLED MY EYES OUT. well about two hours go by and she calls me again and tells me that he wants to know if I would like to see him and talk. I told her that if he wanted to know he had to call me himself. So he did and I decided to let him come over (he lives two hours away) I lived with my god mom and she said he wasn’t welcome in the house so we went to sit in Walmart parking lot and talk. We talked about a lot and he said that basically he left me because he felt like I was giving him wife treatment but I was receiving girlfriend treatment. Which I understand but I told him he should have just talked to me about it. Well I go on to ask him about his ex being at his house. He said she just kinda showed up and wouldn’t leave. So I asked him if he had sex with her he said yes it was a momentary decision and he regretted it as soon as it happened. So ya know I decided to try and work things out because I love him. Well since then I have come to learn that he slept with her three times. And used protection every time( which means he bought condoms because we don’t use them) so if it was a momentary decision and he regretted it instantly how did it happen two more times. And I’m still so scared that he’s just going to leave me again. Was I a rebound but then he realized I’m who he wants? I know he’s not currently talking to her because he changed his phone number and he’s given me full permission to go through his phone. Because I decided to work through it so I just trust him or do I need to follow my brain when it tells me that he’s hiding something and leave? What would you guys do? I’m so confused. I’m sorry for the long post but i don’t know what else to do.