What will happen if I leave US after being illegal for 2 years but I am married to american citizen?

I am 25 years old and currently living in Ohio,my husband and I got married in 2009 and we've been together for 3 years . Our relationship had lots of ups and downs,mostly downs due to his drug addiction,irresponsibility,constant need of cheating,etc . At the moment I turned into crazy,heartbroken person who is left with no choice. I've been trying to get the money to apply for my green card but he took all my savings,I have a lawyer who signed my husband as his client so I can't get any help from there . My husband is having an affair and it's more serious than his other one-night stands and I don't think I can handle it anymore . Currently I am stranded in our own apartment after kicking him out,with no money,bills and without any family or close friends. I haven't seen my parents for 2 years now and I was hoping that once I have the green card I will be able to to go back and see them and things will work out between me and my husband . Unfortunately I don't think I can handle this anymore,I've been waiting for 2 years for him to help me out and I am about to fall apart. I want to leave US but I am afraid that I will be banned from the states since I overstayed my visit. And I know it's probably over between us but there's still hope in me that he might see the light and what I did for him . And me being banned will be just the end! I really think I have future in here,I've been doing what I love (pet shelter volunteering) ,I am asst.-manager at the moment and I really hoped things will work out for us.But now I am at the point I am thinking about suicide,I can't sleep or eat and there's absolutely nobody I can ask for help besides his parents and I really don't want to cause drama. I need help and I need somebody to guide me. What will happen to me? I am losing my mind and need some sort of stability and comfort .I don't have any money ,is there an organization that can help me out ?