It sounds rationally irrational. It doesn't have to make sense, I get it. If you read more threads here in the family and friends forum you will see that this is not all that unusual.
People stay with a spouse or partner for years and it might not be a good relationship, however that doesn't mean there are no good times and that the person doesn't have some merit.
It's going to take time but the first thing I would do is make a list of every terrible thing he ever said or did. Whenever you feel yourself missing him, drag that list out and read it (if that is 10 times a day to start, so be it!).
Originally Posted by
Looking4Clues 
What if the “good guy” side was the REAL him and he just didn’t think I was “enough” to be that for all the time?
Be that for all the time? If he was a good guy he wouldn't be making up some fake persona to present to you. I'm not saying he was, I don't know him but I think we have established he has a drinking problem. He was not forthright with you about that - THAT is an issue, him not being a fake "good guy" isn't an issue here in my opinion. Please let me know if i'm misunderstanding you.
What if he was just a jerk/drank because he was bored with me and wanted out but felt too bad to say it?
Your self esteem is really low right now, based on this comment. This is a pretty big leap to take. He didn't just get drunk one night and break up, he has a pattern of drinking, a well worn pattern. His long time friends and family probably know this as well but they aren't talking about it, for whatever reason. Probably hoping that this time he will change.
Keep reading others stories/threads here in the family and friends forum. While their story may not be your story, you will no doubt see bits and pieces that resonate with you. Understanding alcoholism will help you in that you will start to see some patterns.