Need some advice....

I need some advice.  I cheated on my ADHD boyfriend as a result we are no longer together.  I am still living with him but in a different bedroom.  I know he doesn't want to give up on us and neither do I.  Everything became to much for me to deal with and instead of continuing to try and talk to him I made the mistake of kissing his best friend.  ( I am now in therapy to work out my own issues) I feel like now we are stuck between loving each other and not wanting to go back to the way things were.  We fought all the time about stupid things. To be honest he was very mean to me and I in turn lost patience and said and did things that I now regret.  After having read a lot of good information on this web site I believe our problems steam from his untreated ADHD.  He, last night, started to admit that yes he does have ADHD but he thinks I am using it as an excuse for my actions.  I am not at all and have tried to explain this to him.  What I need advise on is how to continue the conversation with out hurting him and in such a way that he understands that his ADHD has deeply effected our relationship and with treatment we can be together.  Neither of us want to return to an unhappy relationship and I know that once he accepts help for the ADHD we can have a happy life together.