I'm sorry you are struggling.

I've been hiding myself my whole life & I'm still doing it. So I know, as you say, it is exhausting. I made a few clumsy half-hearted attempts to get help. But none of it amounted to anything. I didn't really begin to seriously unravel until I was around 50. And by that time nobody's interested in your problems anymore. The one good thing is, now that I'm 70, I probably don't have a whole lot of years left to worry about it. And I no longer have to function in the world in any capacity. So I just pretty-much keep to myself.
I wish I knew what to tell you as far as where to turn goes. I'm not in the U.K. But, from what I've read here on PC, I have the impression mental health services there can be pretty dismal for the most part. Here in the U.S., if you're young & either come from a family with money or have good insurance, I guess mental health services can be good. But otherwise they can be pretty dismal here too. The state I live in is probably one of the better ones from that perspective.
Anyway... I'm just rambling here.

I mostly just wanted to let you know I read your post & offer you my best wishes. Please take care...