RP, people with ADD/ADHD organize their thinking very differently than people without it. Depending on the severity of it, they can seem downright impossible to reason with. They tend to hyperfocus on certain things and let everything else fall apart. Communication and what would seem like the simplest of social skills are extremely challenging and cause huge anxieties for someone with ADD. And a large percentage of sexual compulsives or sex addicts have ADHD. They get bored and distracted very easily and often look for a sexual outlet. It's hard not to take these behaviors personally but that seems to be a recurrent theme among couples where one spouse has ADD.
Jeni, here's a good resource of articles about relationships and ADD:
I would say to make sure whatever therapist you do see, is familiar and in tune with adult ADD/ADHD.