17 year old son with food issues

My son is about to turn 17 next month. All of his life, he has refused to eat fruits and vegetables, and has resisted trying new foods, although he once in a while does.

The first instance I can remember was when he was about 10 months old, we went out for dinner, and I ordered a plate of mashed potatoes for him because I did not know what else to get for him. He swallowed his first spoonful, and immediately tossed his cookies. That's my first memory of this problem.

He was born a month prematurely, and had terrible colic until he was about 12 weeks. He did not fully open his eyes until he was also about 12 weeks. Fast forward to now -- he is almost 6' tall, but weighs 250 pounds. His diet consists of carbs - bread, pasta, rice, and the occasional chicken breast, or steak. Burgers, fries. He refuses to try vegetables or fruit, but he would drink tons of orange juice if I allowed it. He claims that the texture of veggies and fruit bother him, although I don't know how, because he has never tried these foods in earnest. I am tired of his pediatrician pointing the finger at me saying that I am the one that buys the food, and I am the one that puts it in front of him (the carbs). So if he refuses to eat anything else, then I would be the one guilty of child abuse because he won't eat, i guess.

I am very concerned about my kid, especially since I am a type 1 diabetic. Nothing, absolutely nothing, motivates him. Not even witnessing me go through what I go through. He is a great, wonderful, loving and caring kid. But this all is taking its toll on our family. He has no motivation in school, or in losing weight. He does not hang out with friends. He has not dated. And he is losing his hair, which I feel is because of his diet. I don't even know where to take him for help.

What kind of doctor should i seek out for him? Any other advice? Thanks so much...