How to get my ex back when I'm not ready to give up?

my ex and I were together for 2 years 11 months. he broke up with me a week after I threw him a surprise bday party, because we got in a huge fight, and he finally decided he had had enough of the fighting. I found out a couple weeks later that he had been hangin out with his other ex girlfriend- one whos married and has a kid and is going thru a divorce.

 I was mad at first, but her and I talked a lot over the next couple months, but I think it became too much because it got to the point where id call and if she didnt pick up id keep calling until I got a hold of her.. shes said before that she doesnt mind talking, just not every day.. and that there's nothing going on with her and our ex.  she says she has a kid to take care of and a divorce to make it thru and that getting back together with him is the farthest thing from her mind.. but they do things like go out to eat and go to the zoo and take her daughter to the park.. etc.  
    I know he has feelings for her again, because they shared a lot of firsts together... hes said to one of his friends that he doesnt know if theyre going to hook up or just stay best friends... him and I had a couple heart to hearts, and the last heart to heart we had I admitted all my mistakes and said I was such a jerk to him, but it wasnt just me.. and I said all this oher stuff and as he walked me back to my car he kept looking at me.. and then finally he said that hed think about it.. well we got in a fight a couple days later because I stopped into his ex girlfriends work to see her since shes stopped in to see me at my work before.. but she was busy so I left and he got mad and called me (while I was out drinking) and yelled at me and told me she didnt want to talk to me about him, and that its between me and him not me and her.. so we yelled and I hung up on him a couple times.. 
 then one of my guy friends called and left a message on his voicemail which pissed him off and he called back saying it was over for good blah blah blah.. the next day he sent me a couple text messages saying I F****D up and that I could thank my fag boyfriend (the guy that called my ex) for it.. im like why cant I have a guy call and stick up for me but he can defend his ex?   so later that day I tried to see him at work and he went off on me and told me to get away he didnt want to see me, that im an idiot, and that guy shouldnt have called late the night before.. etc...  all that hurt, but I know he's speaking out of jealousy and rage.  but im not talking to him again til he apologizes. (its only been 3 days so I dont expect him to be around any time soon)

it’s become such a mess and it’s all because I’ve been so obsessive compulsive about it…… I’ve told myself over and over again that I need to back off, but each day it gets harder and harder… im bound and determined to get him bck.. I need some help! we were so good together…. we just had little issues that needed to be worked out….. its not impossible. Anyone have any advice to give someone that isnt ready to give up yet?