Husband has left every September????

New to this site....looking for answers/support. To make a long story short....We have been married 5 years with 2 girls at home. He is the best husband and dad when he is "well" but, every three months we have moodiness to where I get the silent treatment for days or he is at drinking lots and lots of vodka. I call this depression and mania. Sometimes he will withdraw himself to the couch for a couple of nights. In between these times he loves me to death, very sweet, and compassionate BUT all of the sudden over a very small disagreement...he doesn't love me anymore, tired of trying, he's doing us a favor, etc....

For some reason, every September, he has left us for 4-6 weeks. Partying, staying with friends, totally withdrawing himself from the girls and I. He has always come home feeling like a piece of crap but willing to work on our marriage. Last September he left for 6 weeks exactly and even took it as far as to FILE FOR DIVORCE after being gone 3 weeks. He then came home....promised counseling, would go to doctor....whatever it took. I allowed him back after he swore he had not had an affair. Ten days later I find out from a girl that he had been sleeping with her for two weeks...after he had filed. I feel the only reason he filed was to justify what he was fixing to do! I was devastated. Here we are a year later and he has been gone 4 weeks....moving only his closet hanging clothes to a trailer park where he is living in a friends camper. He will not say divorce...just I'm done, my minds made up, I'm not coming home, etc. I've begged him to get the rest of his stuff that is bagged up in the garage but he won't. Only gets the bills and that's it (he's still paying our mortgage/bills/daycare) He loves me and cares for me but not like he should his wife. He came by for the first time 3 days ago and mowed the yard, stayed for 3 hours messing around in the yard, left with bills, BUT....before he left he starts hugging me (of course I broke down), asking what was wrong, if I was ok, and then called at 10:30 that night offering to come stay the night so I would get a good nights sleep....I said NO! Haven't heard from him since.

I just feel the emotional roller coaster and do not think he's serious because of his previous years' actions. I feel as though he "gets off on hurting me!"

I know he is the only one capable of fixing himself but just curious if this could be bipolar or borderline personality disorder??? His grandparents, dad, and sister are all diagnosed bipolar!

I love him to death but I know I deserve better!