I am, and have felt the same as you OP, and have chosen to be on my own now. I have felt suffocated and also been put off by predictability and the expectations in a close sexual relationship, and I get irritated by constantly being 'on show', never left to be myself. I feel 'pressured', I shouldn't have, and it's not been fair to partners, I know that.
I have also felt awful, as I have at the same time really, sincerely loved my partners/husband, but something drives me to separate mentally as I crave my own space, feeling claustrophobic.
I had an unusual childhood, in that I was firstly the only child, grew up without a father, then had a horrible stepfather, and was rejected in favour of half-siblings. It made me independent, used to my own company, not able to 'share' like others do, and I had to develop my own survival/coping mechanisms. No hugs or affection, and so not used to constant, close contact - with anyone. I think I learned how to cope too well! I also have a stress condition caused by the above, so it's probably where the roots of the problem lies - I hate feeling 'pressure', even from those I love.
My ideal scenario has always been [after the first 'honeymoon' years make me feel anxious as I know/assume it is going to end...] to have a partner living in a house next door! Thus being more in control and being able to 'shut off', and recover my autonomy and identity I suppose.
Now I live on my own, quite happily but with some sadness, and have a close friend who I see at the weekends only. It works. I'm celibate but that's fine as I'm older now. I think it is not fair of me to try and have a relationship with anyone, as I have little to offer, I do not expect anyone else to understand my need for solitude and irritation when I don't get it!