ADHD husband engaging in homosexual internet sex

I am totally shocked right now, because last night I discovered that my husband has been engaging in chat room sex with at least one man.  He has apologized and says it hasn't happened that often, but I'm not sure I believe him.  He also blames me for criticizing him so much that he no longer finds me sexually attractive.  We've had a troubled sex life for years, with my husband unable to achieve or maintain an erection.  I've always attributed it to our strained relationship and the fact that I assumed he masturbated frequently and had gotten used to a different type of stimulation.  I never would have imagined he would have anonymous sex online.

I'm sure my husband has ADHD.  He was diagnosed as a child and the doctor prescribed medication, but his mother felt wrong giving it to him. When he cried and begged her not to, she dumped the pills down the drain.  What followed was years of trouble in school, including years of special ed.  He went on to earn two degrees from good universities, but with very poor grades.  At one point he did so poorly he lost his scholarship and had to join the military to afford to finish his undergraduate degree.  He has had multiple conflicts with bosses and has been fired twice from his civilian jobs.  He is under-achieving at best for his intelligence level.  He loses things all the time.  He seems like he isn't paying attention frequently.  He can't budget time or money, and we're in deep credit card debt.  He acts inappropriately in small, embarrassing ways, like taking huge bites of food then chewing loudly and talking with his mouthful at parties.  He will not admit that he has ADHD, only sometimes admitting to what he calls his "challenges" or his "issues."

Our son was diagnosed with ADHD at around 9, and he made wonderful progress on the Dore program.  He is now in high school earning good grades, doing well in sports, and maintaining friendships.  I want the same help for my husband, but now that Dore is available in only a limited way, and with our debt we can't afford it anyway, I want him to commit to Learning Breakthrough. 

I feel totally hopeless.  I am so sick of living with him and dealing with all his problems--messiness, failure to follow through, lack of control in spending.  And now this--homosexual cyber sex.  If it weren't for our three beautiful children, I would leave him.  At one time I loved him, but ADHD has killed those feelings.  Does anyone have any advice??  Does this sound like impulsivity or sex addition, or do you think he's really gay??