I don't think I've ever felt lonely, for a significant period of time, in my life. I'm an only child, following my Mothers death, I was shipped off to a family member who had birthed five boys. Having spent 6 happy years as a) not having to compete for attention, b) having a fairly large tin of lego and c) thrice weekly visits to the local library, I found the whole idea of being around more than 3 folks at once completely horrific. I guess I'd already been hard wired for small groups/me, myself and I by then.
It's not that I don't like company, it's just always inconvenient. Folks want to 'pop round' when I'm ready for dinner, as most of my local friends have tea. So I inevitably get indigestion from either rushing my dinner or only snacking. Or telephone right in the middle of something I'm intently watching on TV. Or taking a bath. Or want milk. (suck on my soya milk, you, you, calf food thieves)
Or to put it another, more brutally honest way, people make my bile rise.
I've lived alone for four years now. I like it. I'd go so far as to say I need it.
I doubt I'll ever be lonely.