Why is my ex acting this way?

(Refer to a previous post about info w his GF/ex)
She broke up with him saying something along the lines of "you wonder if we're going to be together and I wonder if I'm going to off myself. I need to deal with my mental demons alone".
So about month passed and Wewere spending time together working on things. Everything was fine. he told me, looking in my eyes "I've always been in love with you. I tried to hide it and I couldn't. I love you, it was always you never her". he pushed me to tell my parents we were talking again and he even told his mom that he was happy we were working on things because he didn't want to lose me.
A month ago he told me he loved me, and the same day he ghosted me and wouldn't tell me what was going on for a week. I eventually found out his ex then dumped the guy she dated and they were together again. (In this time my gma died and he was willing to go to Indianapolis w me so I wouldn't be driving alone)

we met up one day and he was already angry with me but he couldn't look at me in the eye. Every time I asked a question he ignored it, and looked out the window. When he was speaking he wouldn't look at me. He kept telling me that he wasn't sure if he meant that he loved me. I brought up all the smack he talked about his ex (he said some nasty things about her) and he brushed it off. he ended up deleting me on every type of social media later that day.
A week ago I apologized for acting like a ****, and he apologized too. I forgot to message him Wednesday and he was mad saying "I shouldn't even be talking to you let alone meeting up". I told him I was going to a concert and he was like "please be careful. Please don't drink a lot". He was the one initiating all of the contact. Not me.

Fast forward to today. He's going out of his way to either subtweet me (my friends send screenshots) or comment on the same posts I do saying shitty things.
He only deleted me on social media, none of my friends or family.
What the hell is going on?
Why is my ex acting this way?
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