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).
It just means reviewing and cleaning up your diet and/or giving your digestive system a break - either with a full fast (water only), or limiting what you eat. There are gimmicky cleanses, just like there are gimmicky fitness products, etc..
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).