I know everyone is telling you to NOT get back with him or even try but I'm going to repeat what you've more than likely been hearing.. Don't try again. Please. I'm going to guess that you're into guys who are controlling and overprotective because you're still thinking about that not so great relationship when you're with somebody now who is great and sweet and caring. My sister is the same way. Now she has a baby and nobody there for her. I know you miss him but later you won't miss the ridiculous arguing and manipulation you are attracted to now. You should stay with Jeremy, the guy you're with now. He sounds great.
My sister keeps going back and forth with a guy that is really is caring and loving half the time but controlling, selfish, and unfeeling the rest. It's a nightmare for her and now she has a daughter by him and he does NOTHING to help her out.
One thing that I know is helping my sister in her process of getting over her ex is constantly writing anything down the father of her child does that is wrong. So when she starts missing him again, she breaks out that notebook and reads in her own words what she thinks about him the rest of the time. Helps her get past those times all she thinks about is his good side.
You're lucky though, my sister is alone and thus has to deal with the worry of forever being along versus being with someone that can be a real jerk. You at least have someone and are not a single mother in her 30's.
Now, I don't know how else you get over the ex, but you really need to work harder at that. Whatever you do, don't string Jeremy over any longer. Make a choice and go with it. Obviously, I think Jeremy deserves your attention and not your ex, but it's not my choice to make. Still, seems pretty odd that you're willing to throw away what could be something special with a great guy over a memory of a few good moments with a man you already know can be a jerk to you.
One negative comment about Jeremy though, the man should at least make an attempt to fight for you. Seriously, it's one thing to be a caring, thoughtful, nice guy, but fight for your woman!