Please start gfcf diet as soon as possible.you can prepare; for that please go through older threads of gfcf foodlist.Also send your kid for OT
do not feel desperate. Things will definitely improve. Try to get help from some organisation or institutions that could guide to plan activities for him. Try to get yourself trained for his needs.
Look for his sensory needs, games planned according to his sensory need will attract him, you may consult a occupational therapist for it. Even if you closely observe him, you can interpret his sensory likes that excite him or sensory sound or light or tough that he doesn't like. There are previous post in parentree about sensory games.
Join him in whatever he does is if he is jumping, jump with him, if he is flapping his hand flap your, follow him in everything, he might begin to look at you or respond.
No eye contact does not mean he is not listening
I would like to know few details from you, can you provide your contact number?