I have not been diagnosed with ADD/ADHD nor am I in any way an expert on the subject, however, a long while ago I read a book called No More Ritalin which talked about some of the underlying causes of the symptoms labeled ADD/ADHD. The author of that book has a website with information about adult ADD. Maybe there are some other avenues you can pursue prior to choosing medication that could conflict with your current medication.
Adult ADD/ADHD