How should I handle this situation?

My ADD boyfriend and I have been dating for 10 months. He is 21 and I am 18. The first five months were great. I moved in with him (and his dad because he can't keep a job and afford his own), then he started to hang out with his friends and ignore me a lot and lied to me several times and put himself in situations where it looked like he was cheating (although he swears he hasnt) after that. We worked through it and things got better for a month or so. But the past 3-4 months have been awful. He would leave to go drinking and not come home etc. So I moved back in with my mom 3 weeks ago. He wants to try etc. I broke up with him one morning because he stood me up and never called (he didn't have a phone at that time). He said it was his friends bday so he did that instead. I felt hurt and taken for granted for my patience and understanding, but took him back. We started trying again the next day and he was perfect but I told him in a crying fit, after he refused to have a conversation regarding past times he hurt me that, that I couldn't move on from the past without his help and he would have to be patient with me like I am with him. We went over several ways to work things out and none of them we were both comfortable with, but we both decided we could get through this. The next day I found this site and realized this is what has been wrong. He was diagnosed with ADD as a child and it is now untreated. I have been looking into insurance etc to get him help. Things have been fine the past few days. Last night he went to hang out with his friend (the one who's bday it was) and texted me all night, but this am I couldn't get ahold of him (he has a phone now.) Come to find out he never went home last night, didn't show up to work this am, and hasn't gotten a hold of me or his dad all day. I was worried and scared at first but called the local hospitals and jails and drove by all the bars and usual fishing spots and the friends house. He wasn't anywhere to be found. He still hasn't contacted me or his dad. He is an alcoholic and has probably gone on a drinking binge (he has been sober for the past 3 weeks I've been gone to "help our relationship". Is this day/night due to ADHD or is it just him being inconsiderate and disrespectful. I'm thinking the latter, but correct me if I'm wrong. If it is ADHD what should I do in response when I finally get to speak to him?