Cheating

I’ve been with my SO for 9 years we were high school sweethearts. We got engaged June 2018 and in May 2019 we moved into our first place together. Between the months of February and April 2019 (while we were living with my parents) he was acting very suspicious like not letting me use his phone changing passwords on social media which was weird cause that was never an issue. We got into fights about it he told me I was acting crazy this almost caused us to break up. We kinda fixed things but I was still suspicious about what was going on. At the end of May after a night out I came home and checked his phone I saw that he was talking to a girl on Snapchat. (Which I met at his graduation from the police academy she was a sister of one of his classmates) I was heart broken I couldn’t believe it. I confronted him a couple days later he admitted to everything saying he was talking to her for a couple weeks but that’s all and that he was sorry. I didn’t talk to him for weeks I should have just trusted my gut when I felt something was wrong. Now I feel like he trapped me instead of telling me everything before we moved I found out when I now have no where to go I can’t afford a place on my own. So I am living here trying to fight this battle of insecurity trust issues and betrayal it’s been 5 months since this happened and I still can’t seem to let it go. I have no idea what to do. When the person I was supposed to spend my life with breaks me into so many pieces I can’t seem to go back to what it was.