I understand what you're going through OP, of course through my own experiences. I'm now going back to college in 4 days. This is after being absent from schooling for over a year due to lack of motivation and other issues.
I have been climbing out of the hole I dug myself into (I slowly destroyed everything around me by simply giving up on life) this past year. I've dealt with all the legal problems, gained trust back from people important to while keeping myself sane and motivated myself. I feel much better now that I can finally continue pursuing my dreams.
Just keep your head up and stay on track, don't give up because in the end you will just be letting yourself down. Only you know what it takes to get to where you want to go, so do it.
As for the ADD thing all I can say is it's just yourself making up excuses on why you haven't accomplished your goals. It makes you feel more comfortable believing you have ADD. You could go to a shrink and tell him that you think you have ADD but ADD is over-diagnosed, so he/she could end up prescribing you medication that would mess things up even further.
I'm not saying you don't have ADD, it's a possibility that you do.