There’s a phrase for it Emma, skin starvation. You hear it among widowed folk. And it doesn’t mean a lack of sex. Just the loss of physical closeness between people.
I don’t agree that it’s easier to stay healthy in a relationship (that hasn’t been my experience at all) but the rest is spot on. It’s hard to be single. We’re social animals and not meant to go it alone.
I’m not at all together. I struggle with same insecurities you’ve outlined here. Ignore them and just do the things you enjoy doing. The one that’s right will show up when you least expect it.