Thank you all for your responses.

I think one of the reasons I haven't left yet is because things get better for a few months and are really good and I think he might actually be changing. I'm afraid of hurting him, I know that sounds stupid given what we've been going through but there is still love there and I almost feel like I'm abandoning him. I also dont want to make the wrong decision, and break off the marriage when we could have done something to fix it.

I know it all sounds silly to someone on the outside and I'm not in any way trying to make up excuses for his behavior... I guess it just is hard for me to leave 6 years behind.

I also am afraid that I'm too old for another chance. I know that really sounds dumb.