Am I losing my mind?

Help!  I have been married 21 years and my marriage is awful.  My husband has no focus!  I told him years ago to get tested and if it was ADHD, at least we can build a toolkit to cope and then hopefully manage.  He refused but now with yet another blow up on his part, now he thinks he is ADHD because I told him I have one foot out the door.  And his behaviours are getting worse.  I am used to asking for things 3 or 4 times, doing things myself.  I have every feeling described for a spouse of ADHD.  He has most behaviours of ADHD.  The real problem though is he has a huge lack of accountability.  Not his fault, never his problem.  And now with this discovery that he may have this disorder, I am a nag!  I am so angry and tired.  He is 47, I am 45.  Is it too late to start this now?