kind of hurt and I don't know what to do

So I was in a 3 year relationship but we broke up back in January but we tired to keep working things out. Near the end of this July I found out he wasn't going to change he went a fucked someone else when we had plans and there was pictures. Anyways, that didn't affect me as much as I expected me too because he had a history of cheating. A few days after all of this a guy I work with asked me on date and I rejected it because he was fucking another girl. Anyways, about two weeks later he told me he cut it off and that he wanted to take me on a date. I didn't want to do but my friends encouraged me because the guy had a crush on me ever since he started working there and he would even sneak pictures of me at work. Anyways, point is we hit it off and everything went well. We started dating and everything was so perfect. Fast forward 3 months later everything was still well, we were fine a week ago. We went out and he wouldn't shouldn't about how much he loves everything is going. I was genuinely falling hard for this guy. I caught a lot of feelings. The next day he wakes and acts different we barely speak. We broke up the following day, he wouldn't ignore all my texts and calls. Mind you everything was well he just woke up one day with different feelings. My heart was broken because I don't know what changed. He texted me Tuesday acting as if everything was fine. We got into an argument and I drove to his house to talk. He wouldn't speak but the second I drove if he acts me to have sex. I told him no. We barely spoke ever since. Fast forward Thursday he texted me again acting like all was fine. He knows I hate staying at my house alone while my family is out of town so Friday he came to hang out he was suppose to leave but he refused too and he ended up spending the night he wouldn't shut up about how much he missed me and sleeping with me everynight. I didn't want to have sex at all I kept telling him no. I didn't want it to happen but it did. He kept acting all sweet and wanted me to call out of work in the morning so we could spend the day together. I told him no, he left and kissed me. We texted a little that night and well now it's back to the same old . Ignoring my messages, telling me to leave him alone. What's his problem ? I was an amazing girlfriend and he knew it he said it. We would spend every day together and one day he literally woke up and said Fuck me. Why do men do this?