we've had the same problem for 3 years and what has helped is more activity and drastically changing his diet (he's had chronic constipation since six months) to gluten-free, low-sugar, no preservatives or additives and low dairy.
Also, we are getting the sensory evaluation and many helpful hints in the "out of sync" child- at that age you can qualify for early intervention which is great. Also, we are getting his adnoids out and ear tubes in- maybe your son has sleep apnea or adnoid issues, often those correlate with sensory issues.
Good luck and hang in there!