How the hell do you stop thinking about ur ex.

Ok so you might be thinking what the hell is wrong with this person and this is probably the most basic ass question but seriously I’ve done the most fucked up shit and got back together with him and I know I shouldn’t but he was the only person that I talked too and I told him like everything and even my fucked up past, he kept wanting to talk to me and he even wrote a whole paragraph to me which NO ONE HAS DONE to me then again this is my first serious relationship or was but everything was going well till I messed it up again and I was gonna explain myself then HE BLOCKED ME I will admit I was so like ugh I was so disappointed in myself then I isolated myself and deleted every account so I wouldn’t read old messages butttt I may have looked at his repost today and I didn’t like what I saw I mean yeah I fucked up like big time I know that myself but why am I like this seriously all I do is just isolate myself and don’t let people in like I don’t have friends and now I don’t even have a boyfriend that now my ex and I can’t stop thinking about him so now I here venting cause I have no one else and I’m just a mess well that was kinda good that I let it out of system now I’m gonna go cry cause THATS ALL I GOOD AT.