"In crisis mode with nowhere to turn"

My son is now 10 years old and really struggling at the moment. We have been concerned about his development since he was 6 months old talking to the health visitor, GP (suspecting hearing problems), self referred to SLT at 3, concerns in nursery and now school. Every health professional we have talked to all reassured that he would catch up. In lots of ways he did (walking late, talking late). We were told things like boys are slower, he wasn't talking because his older sister was talking for him, we need to be stricter with behaviour and he needs to learn how to lose. 

His unmet needs in school is causing lots of upset, severe daily meltdowns causing dangerous behaviours, needing collected early, refusing to go and now he is being physically unwell due to anxiety. He has been on the list for 3 years now and told to expect another year wait. I have called and emailed reaching out for any help available and school, and put in a referral for camhs which was rejected because he's on the neurodevelopmental list. I have even reached out to local and national MPs considering flexi-schooling/ homeschooling. He's done sessions with educational psychologist with little progress made. His education is suffering as he's completely disengaged from the classroom, spending most of his time pacing the classroom, under a desk or hiding in a cupboard, he has no friends and now it's affecting his health. In school he is becoming mute at times of stress, he can't communicate his needs and we think he's struggling to even identify his own feelings.

I'm a mum who's extremely worried and constantly reaching out for help, attending courses, paying for aids but every turn we're having doors closed, passed around and no progress is being made at all. Our school is really good in lots of ways, they are caring and understanding, but without a diagnosis their hands are tied about what can be offered. I feel like we are in crisis mode at the moment with nowhere to turn. He is such a kind and caring boy who is extremely intelligent and he is not thriving at all, he's barely surviving. I feel like he's been seriously let down. He should have been assessed long long ago. My biggest regret is taking the reassurance at face value instead of pushing for more early intervention when it could have made a difference.