Advice Needed - What should I do???

As I was surfing the net to look for forums and blogs on marital problems, and ways of handling them, divorces, etc. I stumbled upon this site and ADHD (which is totally something I am ignorant of!).  My marraige of eons years now is on the brink of break-up.  After spending some years living abroad, we repatriated last year.  Since then everything is deteriorating - my husband's attitude, character and behaviour is going from bad to worse.  He is a compulsive liar and I have strong grounds to believe that he is cheating on me as well.  He is forever on porn blogs and indecent chat blogs on his computer.  There is no communication between us now.  He doesn't talk but yells and criticise and on defensive mode all the time.  Tried talking to him but he does not see any problems with our marraige. After reading this blog, I somehow think his symptoms is relative to that of ADHD.  I am presently in the course of deciding whether to walk out of this marraige.  He just doesn't want any discussion on anything at all!!  Help! What shall I do???