Guy's Behavior

Guys, I need your help to see this in other perspectives?

I have a colleague that we have a lot in common. And when we hang it is just fun. He broke up with his girlfriend and asked me to date him. I originally rejected but after 3 times of going out to discuss it I accepted. I totally understand I made a mistake. Obviously I was a rebound. Because I was his friend, literally any time that we met for dating he talked about his ex, in a negative way. And I had to stop him. Sometimes he wasn't really aware he is mentioning g her, so I would ignore and let him move on to the next topic. Eventually I decided to not to proceed and have sex with him. We made out a couple of times that was quite enjoyable. But the anxiety for me was too much. I knew it is not going anywhere and I'm a rebound but sexually I was attracted to him. I eventually asked him to go and find someone else. He told me he is going back to his ex. I pretended that I'm OK with it.(internally I broke down to pieces) He didn't eventually go back to his ex , just kept messaging her. But I like him as a friend not only because we have a lot in common but also because he is really lonely. I have seen him holding his tears and some other sad moments. When it was my birthday, I didn't invite him because he totally forgot my birthday (which I usually don't care) but also I felt he never cared about me. So I told him he is not invited and it is because he treated me as a rebound. Later I felt bad. Because of course he treated me as a rebound. But I let him do that. The person who didn't have self respect not to enter a rebound was me. I let him every time we met talk about his ex. And still went for the next date. So I messaged him and told him I probably was harsh. I'm responsible for decision that I make and I understand everyone does things based on their own benefit. Let's be friends again. He didn't reply. It is a week now. I know I should ignore and move on. But it is hard for me to move on from my friends. Help me what to do to get him back as a friend.
Guys, I need your help to see this in other perspectives?
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