I was 37 when I met DH. Engaged at 38 and married 11 months after that. We've just had a baby, a couple of weeks off my 40th so I'm one of those 'you're not too old' posters
HOWEVER - and I say this in a kind way, I had to work at it. I had to get some therapy as I wanted to sort few of my own issues out, I made sure I had a really fun life and enjoyed my single status to the max. I like to think not only was this healthy for me, it helped me meet a similarly upbeat person who wanted the same things.
Don't get me wrong. Online dating is a huge effort. It can be fun but you've got to be in the right headspace and dedicate a lot of time to your profile, chatting to guys, weeding out the genuine chap and of course dating too.
I'm not into American dating guru type sites that are all 'gamey' but this chap really helped me suss out what I wanted and how not to waste my time - cos let's be honest at 37 I didn't have time to waste!
www.evanmarckatz.com
There's loads of free advice on his site. Read all his blog posts.
BUT you've got to have the right attitude and be in it with a positive mindset or else you'll just keep on self sabotaging.
You seem to have a lot of worries but resistant to making changes. You can totally have what you want, or at least a damn good stab at it and a lot of fun in your life but you've got to really want it, not keep deflecting so you don't have to deal with the disappointment (and they do happen along the way).
Good luck. I do hope you'll take something from this thread that will kick start the changes you need.