Most Helpful Guy
Why in the world would you ever take a guy like this back in the first place? All you'd be doing is teaching him (or confirming to him) that he can cheat on you with impunity, and even break up with you, and you'd patiently wait on his back burner until he was done with his fling, and you'd take him back. You'd be acknowledging that you're okay with being his "second choice." Is that really okay with you?
in my opinion, the best thing you could do is grow some self-worth, cut off all ties with this guy PERMANENTLY AND FOREVER, and move on with your life. There are plenty of guys in the world who will treat you much better, so why encourage and enable some guy to treat you like crap?