I'm in the same boat. The longest relationship I've ever managed is around 2 years and that was over a decade ago. That did produce my DD which I must admit made a massive difference to me. I do have a panic every now and then about how I'm going to cope whenDD leaves home, which won't be long now...
Anyway, I digress. I hear you. It's hard being alone. All the crap about 'it'll happen when you stop looking' lines are patronising at best. Ignore.
I have seen women get married, divorced and married again in the time I've been single. And it seems really unfair that they can achieve what I've never been able to do. I genuinely don't know why it doesn't happen for some of us.
It isn't you OP, you're doing nothing wrong. Your life sounds interesting and you sound like someone lots of us would be happy to be friends with.
You can of course stop trying to find a partner and be perfectly happy alone but deep down I don't think that's what you want to do.
I think that what often happens is that people get used to you being single, so they assume that's how you want to live your life. Have you told all the lovely women you do knitting/volunteering/crafts with that you're looking for a partner? Let them know... they must have cousins, brothers, sons, friends sons, who are single? Can you let them help you find someone?
I'd also seriously consider a matchmaker. Not cheap but they can do the hard work of finding a suitable partner for you, rather than you having to trawl through the time wasters/the great unwashed on online dating.
36 is still young in my book. I've got a good 20 years on you OP. The older I got the more vocal I got... my advice to you is to get more vocal now. Tell your friends you don't want their boyfriends tagging along. Tell your friends/volunteer groups/crafting friends that you're single and want their help to find a relationship. Tell yourself how fabulous you are. Tell yourself that it's ok to be single.