My 6 yr old son is more than just a picky eater...?

My son will only eat the "four food groups"-pb&j, cheese, chicken nuggets, and pancakes/waffles. Sometimes hot dogs on a good day. I am so worried about his health and not getting enough vitamins/minerals. He will literally gag if given any kind of meat, or anything green. Please help! He has been diagnosed with sensory intergration disorder, and the doc told me he won't eat other foods because of the way they "feel" to him-he has issues with texture, not taste. Now, my husband thinks this line of reasoning is "bunk" of course. I have fought, pled, begged, even punished him for not eating what is served and I am forced to make him special meals. Please help w/ suggestions!