What should be done in my situation?

Well seems like he treated you poorly to begin with, you left him, he realized what he was missing decided to change only til he got you back!
Now that has you back, he can go back to treating you like he did to begin with!

My best advice to you is as follows…

1. have a real heart to heart with him, one on one face to face no letters, no phone no emails…make sure he understands what you mean & that you refuse to be in a relationship like this treated like some sort of possession.
   Stand your ground girl, tell him like it is…Either you are with me & if so then prove it… or leave me the hell alone!
2. who the hell is this girl you refereed to when he said he was with that girl! if he is playing around stringing you along while with other girls you seriously need to consider that its over, been over & can never be again! he is disloyal & will continue this behavior in the future. Ask yourself do you really want to be with a guy that will treat you this way or would you rather be with someone else that will treat you like a queen!?

Personally that is why I never go back on sloppy seconds! If it didnt work the first time, obviously there is a reason for you breaking up with him in the first place!

As for revenge or hate, girl if you are already dont trust him as far as how he feels about you…that is your answer for moving on! Trust is the number one thing in a healthy relationship…no trust relationship dead & over!

hope this helped, good luck!