During your "doctor recommended breaks" - try doing diet cleanses, elimination diet. Many foods, very common ones - wheat, dairy, eggs, soy, potatoes, almonds, etc - can cause ADD-like thinking through irritation (that you may notice or not) in your intestinal tract, etc.. Then there is also childhood emotion repression that could be a cause to ADD / scattered thinking. Food and past trauma are two things to always look into if someone's having difficulty. I always suggest a good dose of yoga with a regular yoga practice to help with the calming / releasing endorphines, serotonin, etc. - reducing baseline stress levels.

Edit: Oh, and also, if you ever had painful ear infections as a child then look into http://www.aitinstitute.org (sound / auditory re-training), or if you've never had your vision properly checked out -- you should be able to see clearly / things in focus with your eyes relaxed, if you're straining them then it means your brain/mind is actively concentrating to focus, which then will take your ability away to focus on other things fully (leading to ADD symptoms).