Help get my ex back

3 weeks ago I went to meet my family after graduating high school just to find my boyfriend of 5 months was no where to be seen. We had fights for the days leading up for an array of reasons but the day of was great. I immediately knew something was wrong because he drove in with us. I asked my mom why he wasn’t there and she informed me he had a police officer drive him back to my house so he could get his things and leave. I immediately called him and he told me I cheated on him (I never did). I asked him why he thought this, and he told me he went through my phone and saw messages between me and a friend where I told this friend that I missed him, loved him, and didn’t want to ruin things with me and my boyfriend. He also said that he called his friend during my graduation and his friend told him that I was cheating. I told my boyfriend everything and I didn’t. I explained I do miss my friends and I tell them all that. I told him that I did say I love you and that was wrong, but it was only a platonic way and as soon as I thought I shouldn’t be saying I love you to a male friend. I stopped. (Which was 1 week into dating)And lastly, I told him how I said that I didn’t want to ruin things between me and my boyfriend because I didn’t know how he would react to having male friends. I did this all screen sharing, showing me blocking my friend. He told me that I was lying. I told him when I get back to the house and have Wi-Fi. I will show him the messages because they weren’t working at the time. When I got home and checked, the messages were gone it said Instagram had an error. I told him this, and he obviously didn’t trust me I tried constantly to talk to him about everything but he wouldn’t listen. I wrote him paragraphs explaining everything again and again. Nothing worked a couple days ago. I wrote him one last paragraph and sent it through Discord because that was the last platform he hadn’t blocked me on. He didn’t respond, but I got a friend request. It was a girl I added her back and I immediately went to see if some of the same name was following my ex. My heart dropped seeing that there was. I messaged her asking about my ex. She lied and told me that she had no idea who that was. I sent her a screenshot of her profile with her response being I’m pretty aren’t I? I immediately responded with you are because I’m not gonna bring another woman down over a man. She got him on the phone and me and him talked. He called me the B word and told me that I made him spend all of his money on food for me, which I had never done. He kept repeating that I had cheated on him and finally hung up. The girl messaged me again, saying that he never cheated on me.(which was never even in my mind.). And that they aren’t talking or dating. I went on with my life trying to get over him, but on Wednesday after a concert, she messaged me saying she lied and that her and my ex were talking. Sending photos of them together and calling me very mean things. I want to say that I don’t hate the girl. She only knew what Mason was telling her and that’s not her fault. Then yesterday one of her TikTok’s comes up on my for you page. It says that she got asked out and blocked the next day. I went on my alt account and stalked a little bit. Finding out he did block her. I messaged him on my account saying I wanted to talk to him, but I haven’t gotten a response. he was my first and I really don’t wanna lose him. If anyone has any tips on how I can try and fix things with him please let me know .