To me, it sounds like your son may have had a stroke in utero. (Strokes in utero are not uncommon. I personally know a number of people who either had a stroke in utero or whose child had a stroke in utero.) I personally would be inclined to take him to a neurologist to get it worked up because, if indeed, he did have a stroke in utero a blood-clotting disorder may have been the cause. If you have a blood-clotting disorder, you definitely want to know because for many you can take medication to prevent you from having strokes, etc.
As a mother of children who have special needs, my heart goes out to you. "Cannot move the left-side of his tongue," "much stronger on the right side," "stroke," "cerebral palsy," etc. are all scary to hear. At the same time, you likely will simply continue to do what you presumably are doing or have done: ST, OT, PT. I hope you can take heart that if it has taken 7 years for these symptoms to be identified then the effects haven't necessarily been devastating. In short, he's started out with a pretty high base from which to work. (In contrast, if he was unable to move his left-side of the body at all, he would be starting out with a lot more work to try to do and a lot more to overcome or adapt to.)
I hope that helps!
