Most Helpful Guy
Um, I was in a similar situation only I'm the guy.
I was slightly depressed and emotionally unstable and that kept hurting my ex, she dealt with it in a really cruel way by dating others. Anyway, I was ready to do WHATEVER was required to work it out, if she just stood by me and gave me time.
spoiler ending: she didn't and her feelings for me wasn't genuine because she said she loved me and wanted to figure it out but used one argument about her dating others to bail and go exclusive with another guy she saw, basically I got played
Most Helpful Girl
No, you shouldn't.
Something that helps me when I have a personal dilemma, is to try to think of it from an outsider's perspective. So, if a friend of yours came up to you and said "hey, this guy who has treated me badly in the past, who has issues, and who has broken up with me multiple times before, is now back and saying that he'll change. Should I take him back?" - what would your response be? Surely you would tell your friend no, and that nothing good will come out of it, that he's not worth her time, that he'll just keep breaking his promises and her heart.
By thinking of it from a different perspective, it suddenly becomes crystal clear. So, why would you tell a friend to leave him, but tell yourself to give it another shot?
He's not worth it. You've given him multiple chances, and each time he has failed. I admire his will to change, however, he should know that he has already messed up his chances with you and that both you and him should move on.