Blah what a waste of a young lady -_-. You can do better then that. Let me tell you something, EVERY (ok not every, but quite close enough), most girls who have been in a close relationship at least once have at least felt the same thing you did. Where they just cannot believe they can move on and he is the only one for them. Bull. Simple bull. There would be hundreds of millions more depressed women in this world if they never moved on from their first love. Bluntly and somewhat harshly speaking (sorry, I'm not gonna be too sentimental sounding because I have a test tomorrow on a saterday!!!) Attachment is a blindness, that is all, whether or not it is directed to somebody worth it, it does not matter, it still creates this barrier between your instincts/intelligence and the heart. These are the kind of cases where you should NOT let your heart and emotions get to the matter, take a deep breath and think things through with your brain.
If he really is like this, he will ditch you inevitably. Or, he will wed you and abuse you for the rest of your life. Are either of these what you desire? If not, hopefully not, you will move on. But I have a feeling you won't, as many of my girl friends did not and continued to feed so much energy into their undeserving man, which they all came out heartbroken anyway since the guy left them anyway.
So what I mean is this:
1. Either you try to cling on and stick with him, take more mental abuse, begin to crumble and have your mind shaped into thinking bad about yourself (low self esteem is common), and then he will leave you, leaving you more crumbled, with a twisted mentality due to the pain, and taking months if not years to heal. Meaning you have spent many hours/days/months/years trying to cling on for nothing and you will be in even more unbearable pain.
2. Or you think rationally, look at his personality and see if he can change (use your brain, do not let hope blind you and go "i think he can really change for me!"), if he cannot, move on, take your time licking your wounds and heal, which may also be months or years, but you will be far less damaged mentally and have saved time.
If you take option 2. I guarantee that once you have gotten over him (which you will unless you decided to become a hermit and posted pictures of him everywhere from the ceiling to the toilet paper), you will be much happier knowing that you did not stick with something that you would regret. If you take option 1, I cannot say if you will ever recover from a potentially traumatic ordeal, but if you have healed after some time, you are going to go "jeez why the heck did I spend so much time on this guy, I could have used all that time I wasted being depressed to better myself or catch up with friends or maybe found a better boyfriend, or etc, etc, etc.
Sorry if I seem harsh, I kind of say this without emotion because I feel like a tape recorder saying this to my girl friends over and over and over and over again. They rarely listen and go "yea i know... but" because they let their emotions get to them, I always hear "I'll give him one more chance". Each and every day, their hearts get ripped a piece to a piece till all I get to see is them crying or with a fake smile telling me they are ok =(. Don't let that happen to you, it saddens me seeing my friends going through the same things, nobody should deal with such pain in a relationship.
Be among the wise!