M.W.
I would try to find a chiropractor in your area that specializes in children. www.ICPA4kids.org is a great place to do that. It could be some sort of neurological component that he doesn't know what to do with it. A chiropractor and check to make sure the nerves from the brain to the mouth and throat are working and correct any interference. Also - having him crawl can help remind the brain how to function properly. It's call the "cross-crawl" technique.
Hope this helps!
I forgot to mention! Pay attention to your sons bowel movements. Frequently if there is a constipation problem children will not want to eat. They should have a bowel movement at least once a day at his age if he is off of breastmilk.