Headbutting

My almost 3 year old has developmental delays and suspected autism, is nonverbal and doesn't seem to understand most of what I say. Because of this he gets frustrated easily and lashes out, smashing his head into whatever hard surface he can find, or if i'm near him my face. I have been told that when he starts talking it should settle down, and to just ignore it but it's not doing much good right now. I have put padding around areas where he would often hit his head, but as soon as he realised it was cushioned he started smashing his head onto hard floors, and whatever else he could find that wasn't cushioned. He always has bruises and bumps on his head, some of which turned into sores that took months to heal because he would just keep smashing his head and reopening the sores. I tried taking him to child health nurses and doctors but I keep being told to just ignore it because its attention seeking, or that its frustration etc and it will pass with time.
He has given me black eyes, nosebleeds, busted my lip and caused so many bruises on my face that people have suspected my boyfriend is hitting me. I've tried to ignore it, told him no, I have tried to redirect his attention, and putting him in his room when he headbutts me but its not making a difference. I have been trying to get him to see specialists but apparently it's a long waiting list and he won't be a priority until he starts school. I don't know what else do.