My (18 F) boyfriend (26 M and technically ex now) is convinced I'm cheating on him but I'm not. How do I convince him when he won't respond to me at all?

I'm sorry if this post is a mess. Everything feels like a blur.

Every year I go to prom with my best friend. He has a girlfriend and there's nothing going on between us at all, it's basically a tradition in our families because our families are close like we are.

Me and my boyfriend have been dating for 2 years and it's long distance because we live in different states and met online. This year, close to prom, we got in an argument over another woman. There was this woman trying to convince him to break up with me and I was upset because he said he was tempted. We didn't talk much after that. I didn't reach out to him and vice versa.

I spoke to him the day before prom because I just wanted to get past the whole thing. We didn't talk a lot because I assume he was busy. Now a lot has happened these past few weeks. A few of my relatives passed 2 weeks ago and I had to attend a funer for one of them on prom day. On that same day, I just got into a huge argument that resulted in me losing almost all my friends, so I wasn't really all there and even today I'm not feeling it.

Like I said, me and my friend go to prom every year. Last year he even knew about us going to prom. I had no pictures on my phone for myself so I asked my family to send me pictures. They didn't send me any pictures of me by myself and I don't think they even took any, so I just picked the ones I thought I looked the best in.

I had already sent them to some of my friends so I wasn't thinking when I sent them to my boyfriend because I had a lot on my mind that day. One of the pictures had my friend's hand on my waist. It's not a pose we chose, it's a pose the people taking the pictures told us to do. I didn't think much of it and I will admit it was dumb of me to send it in hindsight.

Right after I send it, my boyfriend broke up with me and accused me of cheating on him. I was confused and we ended up arguing. So I tried sending proof that my friend has a girlfriend and there's nothing going on between us but nothing seemed to work. After a while, he just stopped responding altogether even when I provided proof of them being together and us being just friends.

If you're wondering where the woman comes into all of this, he said how it was suspicious how I felt bad after he left her for me. But that was never the case. I felt bad for her because he does this thing where he ignores people just for kicks because he claims he's an "emotional sadomasochist" or whatever that means. I felt bad for her because he's done the same exact thing to me after his dog died and I would check up on him, then he broke up with me and made up something about having opps and that he had to break up with me "for my own good".

Now that I say that, that's what he's doing to me currently. No matter how much I try to get him to talk it out and look at the things I sent to prove I'm being loyal, he's just ignoring me. He won't block me and I know he sees my messages and calls, but he won't respond at all. I don't understand why he won't hear me out when I'm trying my best to resolve this and set the record straight.

TDLR: My boyfriend thinks I'm cheating on him after I sent him a picture of me and my prom date. How do I fix this?