Sorry it might be a boring question..are ADHD and cheating related??

hi, I'm very new to this site. I have a boyfriend who I found out from our couples therapist that he has ADHD a year ago. I read about ADHD and now understand why I was always angry at him about small things and he seemed to not care about me and our little boy safety. I.e leaving the house door wide open when he went out in the evening while I was sick in bed with a breastfeeding 6 months old and drive recklessly with our child in the car. You know all the crazy little and big things that ADHD people do. Recently, I found out that he has been having an affair. I havent address it to him (yet) and he still doesn't know that I know. He is still in touch with her and planning on seeing each other again as she lives abroad.  I have been seeing our therapist on my own about all of this and he told me to not say anything yet. He said my bf will get bored of this new toy and therapist said she isn't the only one my bf is playing around with. And I know also that she isn't the only one as I saw messages from another girl popped up quite often saying how she misses him. I try not to read everything as they hurt my feelings but I look briefly to keep my finger on the pulse to see if they r flings or more or how long is it going to last.

My question is are they related? ADHD and infidelity?? I read melissa's book but doesn't say much about affairs and online has mixed info of yes and no mostly nos. I also think my bf has narcisstic personality disorder like his father. The thing is I don't want my therapist or myself to give him an excuse to have an affair because he has ADHD. I'm still thinking whether to leave or stay. I'm not sure how long I can play calm and cool for. I have a little 2 year old with him who loves his dad very much and he is also a good father, as good as an ADHD can be and works very hard. I could put up with all of his dirtiness, scattiness, forgetfulness but affairs I'm finding it hard to cope. At the beginning of the affair he had been going around telling some of his close friends how much he loves her and wants to explore her. And then expect it to be hush hush. I just couldn't get my head around it all as to why he does this!