Struggling - No One Will Help Me - Feeling Suicidal

I think I am autistic. I am having my assessment next Tuesday. 

My problems started 6 months ago when I saw my GP as I have been struggling with quite severe anxiety issues all my life which have gradually got worse especially over the past two years. He refered me to IAPT for a 4 week CBT course. All was well for the first couple of sessions until autism was suspected as the cause. I had always suspected that I might have autism but at the time didn't relate it to my anxiety issues. The final sessions Tgot completely derailed as I tried to come to terms with this. The course duly finished and was told by the facilitator that as I was still struggling I would be put on the 6 month waiting list for an intensive 12 week course of CBT. A referral was also done to the autism dept for a diagnosis (3 month waiting list). I went away with my anxiety levels sky high knowing I had to try and struggle through on my own for 3 months. After a week of panic attacks at work I realised I couldn't so on struggling so decided to ring IAPT because surely they have a duty of care and an open door policy? How wrong I was, I was told they couldn't help and to go back to my GP. Next day I did go to the GP and he was shocked that IAPT wouldn't help and sent them an e mail asking them to contact me. I waited a few days but didn't hear anything by now I was starting to feel suicidal so phoned IAPT and spoke to the receptionist who said that someone would phone back ASAP. 3 days later they still hadn't phoned - I was phoning the Samaritans by now. I phoned IAPT again and did actually get to someone - bad news though - no they wouldnt help. I asked them when the 12 week course was likely to start and was told that i wasn't on the waiting list and my CBT person shouldn't have told me about it. Went back to the GP to ask that as IAPT were refusing to help with my anxiety issues who else is out there to help? He had no answers so I ended up being signed off work for 4 weeks. During that time Occupational Health got involved and I received 4 counciling sessions by phone(better than nothing) I also contacted  PALS to try and get some help and they managed to get me enrolled on a 4 weeks anxiety course run by IAPT. After the first session we had to fill in various forms (GAD 7 etc) and a few days later I received a letter from IAPT saying that they were concerned and that I should contact my GP ASAP to get help. I went to the GP and he rang IAPT, they said they wernt prepared to help me until ive had the results of the autism diagnosis.

So Ive been hung out to dry by my GP & IAPT. Ive got no help from anyone. I am a postman and yesterday I had a slight accident in my van which has made things even worse.

I know CBT might not be effective but it helps me (had a course also 20 years ago which helps a lot)

I am so stressed out by the past 6 months and I have lost all hope of ever getting my severe anxiety reduced.

Me moment autism was mentioned all help was stopped. I feel like giving up on life