The long wait for assessment

I was referred for ASD assessment in December 2016 and told I could expect an appointment in Summer 2017, maybe earlier. Almost 2.5 years later I'm still waiting and I feel like the anxiety and uncertainty have taken over my life. 

I know its NHS waiting times and it's not their fault but not having a set date is stressing me out so much. Every time they tell me 'your appointment will be in April' (for example) then I get myself all worked up for it, I check the post every day from the 1st March and nothing comes. So then I call them and get told it's now not going to be until May and the whole cycle starts again. It's hard not to think about it when it's always 'next month'. I'm currently set for June/July assessment date.

I've had a lot of change and minor stresses going on in my life recently too, which hasn't helped. My GP has put me on anti depressants and has offered to prescribe me something to help me sleep if I feel I need it. I'm trying different things to try to relax a bit but i tend to get very obsessive over things. If I could afford a private assessment I would. I also feel like I can't talk to anyone about it because if it turns out I'm not autistic I'll feel very silly and I don't want anyone knowing about it! 

I know a lot of you will have experienced a long wait for assessment and I'd like some advice on how you got through it.