Dear Wiish,
Welcome to this board. I'm very sorry for what you are going through. I can relate to most of what you have experienced. My N H of 23 years (we have been separated for 18 months and hopefully are close to divorce) started having an affair with a younger, married woman that he met through work. He is not a drug addict or alcoholic that I am aware of, but he has always been a party boy and one of his reasons for leaving was to have more fun. My husband's addiction is a sexual one. Not having sex with me--that hardly ever happened--but using porn and having sex with himself. That has been going on for most of our marriage, but I had no idea. He was lying about his disinterest in sex, blaming it on being tired, stressed at work, medication, blah, blah, blah. I am attractive, in shape, still weigh the same as I did when I graduated from high school (I am 54 now) and take good care of myself. He was the one with the weight problems, but I never said anything or gave any indication that it bothered me. Of course, once he got the girlfriend he went on a weight loss program, started working out, whitening the teeth, tanning and of course, the dead giveaway, bought new underwear and went from briefs to boxers.
I was shocked just as you were by the announcement that my H wanted to leave our marriage. I lost 12 pounds in 6 weeks because, like you, I couldn't swallow food. It wasn't until I got on some anti-psychotic drugs, that I was able to start eating and regaining my strength. I have 2 children, 16 and 20 who spend very little time with their father and his support comes in the way of money only. My daughter got confirmed at church tonight, and he did not bother to show up.
I hired the best attorney I could get (my H wanted to hire him, but I got to him first

) and we're still fighting through it. In fact, we go to mediation on Thursday and I am asking all my friends here to say a prayer for me that I get what I am deserving of and I can walk away and be done. He continues to lie about his business income and can get away with it because he is self-employed and in business with his father.
I could relate to much more of what you said, but I think you get the idea. I will say that life does go on and things get better and you will eventually realize how much better off you are without him. All cliches right now, but true nontheless. I have started dating again and see hope and light at the end of the tunnel. I pray you do as well.
God bless,
Brigid