Hey C.,
My son is now 10 yrs but starting at 4 yrs we went through the very same stuff. The only thing he could do for a longer period of time without any direction was TV and computer. Not the best activities, but ones we used when needed.
We had his pre-school teachers suggesting everything from possible ADD and ADHD to specific diets. He is not, nor has he ever been, ADD/ADHD. We sought our referrals initally and frankly 3 out of 4 professionals told us that he would be too young to test. One of the factors in assessing ADD or ADHD was how well he controlled his external environment. At that age he can't, nor should he, to the degree that testing would require. Needless to say, it was a rough year or so but we waited it out and he "just grew out of it". Because it consumed out lives for a good time, I can remember exactly the week during the summer before his kdg year when it "just kicked it".
Now 4 yrs later he is a great, socially acclamated, educationally gifted, athletically involved boy. Now that is not to say he doesn't get into his fair share of mischief (yes, we get a call from the principal every Spring before school's out letting us know he was disruptive in class - I'd never tell him, but who wouldn't be if you were stuck inside most of a beautiful Spring day?!!?). Most all of his attention seeking behaviors he did at 4 and 5 are pretty much gone. He has gone into the next phase - verbally challenging every decision or consequence we give him. UGH!! Such is life??!?!?
All this to say...stick with it. It DOES get better. If he is anything like my son, he just needs time to mature and grow up. It's tough living through it, but when it all comes together you can look back and smile.