ASD and picky eater

Hi,

My son is 4 years old and is autistic,he got this diagnosis when he was 19 mths old as PDD-NOS.He was eating good and all his milestones were delayed just with 2 months when he was 18mths old he had high fever of 104 degrees and after that he regressed totally with eating.he has lot of eating issues and regresses often with eating.we did lot of feeding programs such as food and fun,STEPs rite now we are on waiting list at Baylor.rite now he is having just 2 glass of milk a day,he feels hungry puts food in his mouth and spits,this is going on since 3years,it is so frustrating for us every day,can some one help us what to do.he keep chewing on papers,his shirt.I am doing massages but that is also not helping much.
Thanks