I am reading Dr. Hallowell's book SuperParenting for ADD. He describes the Kolbe assessment, which is not about ADD specifically but can be very helpful for people with ADD (he has it).
It helps you understand your native strengths, and how it impacts the way you interact with people with a different set of strengths.
http://www.kolbe.com/

Consider if getting a definitive diagnosis will alter your life much? You may want to assume you have some of the traits and then employ some of the tricks used by successful people with ADD. Definitely find out how to leverage your strengths that can come from having ADD.