I was a rebound and I’ve never felt this awful – What can I do?

So I (23F) met a guy (22M) about 6 months back, and I had no idea he was recently out of a relationship. I didn’t expect to have any kind of relationship with him, as I’m quite a reserved person and often don’t even notice if there’s romantic interest from someone. However, he pursued me hard. We were so similar and had so much chemistry that we got along amazingly, and we eventually started dating.

Everything was perfect, we were together for 3 months (my relationships usually last at least a year). He would bring up his long term ex in a negative way without me asking, and I would brush it off because I figured he was just venting. He made me feel really protected in a lot of my personal issues, and he promised me that he would be here for me through everything I was going through. I believed it because of how consistent and considerate he was towards me. I even lost my virginity to him, something I’ve never been comfortable enough to do with exes to the point I thought there was something wrong with me. He made me feel that safe.

One day, out of nowhere he broke up with me. I was devastated but calmly left his house and cried at home. He told me he wanted to try again with his ex and that he still loved her. He tried to get me to stay friends, but I feel so hurt by this that I don’t want to speak to him, and I can’t watch him be with her while I’m going through this. Now they’re together like nothing happened, despite all the issues he said they’d had before.

What’s killing me is how I still can’t sleep or eat despite the break up being almost a month ago, and the relationship being so short. It was the most intense and short relationship I’ve ever been in, there was a lot of passion from both sides and I’m wondering if that’s why this is so hard to get over. I’m still coming to terms with the fact that he was my first time, and I regret it so much because I feel used and I’ll have to remember this forever. I just want to move on, I can’t sleep without taking medicine and I just cry at random times throughout the day. How can I move on and stop obsessing over this? I keep hoping he’ll come back, even though I know I wouldn’t trust him. We have no contact and I stopped checking his socials but I still feel depressed.