Running in circles

The past few weeks have been extremely stressful and frustrating. As I have mentioned for every step we make forward there are two steps back. Now it may be three. Robbie has been tough. He has not been following direction- a skill he was good at. He has not been getting good reports from school- which is odd. He has not wanted to get dressed in the morning- something we thought we had overcome. He has not been going to the bathroom on the toilet- a behavior we had mastered. He has not been sleeping regularly- an issue we've always had. Most importantly to me- he has not been "present" more of the time. He is in his own world. Why? I wish I knew.
We have changed his diet and removed the items he is allergic too- via the allergist. ( Milk, eggs, egg whites, soy, peanuts, and pineapple.) One would assume Robbie would be responding positively. He was never a big dairy eater to begin with. He hates eggs and won't go near peanuts or peanut butter- so the diet isn't that different. Why is he going nuts?
Over the next few weeks we have appointments with the developmental pediatrician, the neurologist, the allergist, the regular pediatrician, his school, and I think I am calling the "healer" we saw in the beginning. I am truely at a loss. We were making progress. I pray this is a minor set back but it scares me.