ADD and a failing marriage

I just joined this site and boy am I glad I did! My husband and I have been married almost 2 years and have been together for 6. I always new that he had ADD and it was never really an issue. When he and I first started dating, he was on his medication for it and he was everything I wanted in a person, (fun, sweet, family oriented, responsible, caring.. the list goes on). One day he stopped taking his medication and just changed, became lazy, irresponsible, never wanted to be around his family, was doing bad in school, making bad decisions. I contributed it to his age (17), and that he was going through a rebellious stage. He and I were young, I didn't like it, but we didn't have any responsibilities so I never really new the impact it would have. I ended up getting pregnant and that's when I new that it wasn't just his age, because not even having a child would make him motivated to do the right thing and be responsible. Well, one day I had enough of basically being a single parent! He wouldn't work, made crappy decisions, and was not taking on the responsibilities a father should, young or not. I left him and he decided to do what's right and joined the Marine Corps. He and I got married, we were 20 years old and I thought "this was it! he was finally going to grow up and do what's right by his family!" And he did, for a while. He was doing what he had to do because he was forced to but I knew if given the opportunity, he would go back to his old ways. I did everything around the house, and getting him to take out the trash or unload the dishwasher was a chore in itself. I would nag him which would just bother us both because he thought it was annoying and I thought why can't a grown man just take the trash out when I do everything else! Well the military ended, and we moved back home and I was scared to death that things would go back to him being unmotivated, lazy, and making horrible decisions without taking in to account how it would make me feel. Well, they did go back. He would be out all night with his friends hanging out, not waking up for work, not answering the phone, barely spending any time with his daughter. And I would get angry and say "You are married! You are not a teenager anymore, you have responsibilities, and me being your wife you have to take into consideration how the things you are doing makes me feel!" And he would say "you're right, I will try to be around more" but the next day he was doing the same thing. He would tell me he knew and would do things differently but wouldn't follow through, and he would never stop and think how it was hurting me. So here we are, separated because he got sick of hearing me nagging and fighting with him about it, and me sick of actually dealing with it. And the other day, he posted an article on his facebook about "20 things to remember when you love someone with ADD." I read the article and it described him and our situation to a t. I always new that he was ADD, but I had no idea that it was possibly a contributing factor to his behavior. I thought that he was just lazy and didn't want to grow up. Now that I have read a bit about it, I feel like I understand him more and want to find ways to fight through this with him. I want to better handle these situations and I want to better understand my husband, because I thought he just didn't care. I know in the end, he makes his own decisions and he can't blame all of his bad choices on having ADD, but I want us to find ways to help each other thrive and be the best that we can be. So my question his, how do I handle him?!