Wumpy, you sound like my double, except I am nearly 20 years older. I too could never decide what to do. With most jobs I was challenged for awhile and then found them to be boring. Then, without thinking, to make them more stimulating, I would find myself in some sort of trouble. Never doing any harm. I too have a degree, in psychology no less. And I feel I am very intelligent too.
Depression has been an unwelcome companion for a very long time. I am on meds, now switching from Adderal and Welbutrin to Celexa and Dexidrine. When I was a psych student I was very interested in the connection between behavior and neural pathways. Somehow I was able to focus enough to learn that seritonin was an important neurochemical that would help with my illness. Even before I was in college I would take Tryptophan and Tyrosine both precursors to Seritonin. And they helped.
After going through a horrible divorce I found myself doing exactly what you are trying to do, start over. It has been and still is difficult. The symptoms of ADHD never go away and I still struggle with memory problems and getting along with my fellow students. What I find especially frustrating is that no matter how hard I study for written tests, I always do average and the get depressed for not being able to live up to my capablitlies.
If I were able to offer any sort of advice it would be to do as emwell stated above and read as much as possible about Adult ADD, ADHD. Then begin to look at your strengths. For me, it was my creativity. So, I am now pursuing a career as a chef. Although this fits for the creativity side of me, the frustrations of school, memory, and trying to understand what French Chefs are trying to say in broken english is difficult.
I have no idea where I am going to end up and that causes the same anxiety that I think your feeling. Hang in there your not alone. Take an art class, drawing really helped me as did photography. Good luck
Joe