count your breaths in your head.. 1-10, then repeat.. each time you notice your distracted start over, eventually you'll train yourself to better control your thoughts. I've actually gotta get back to meditating, I pray, but have had a lot on my mind so sitting there very long has been tough lately.

Also, I see you've never been diagnosed with anything.. don't be afraid to go to a doctor, I'm sure they could help you the best.

Best of luck.