I something of a loner, and I identify as polyamorous by nature.
I'm a total homebody, and I much prefer a quiet evening with myself over a wild party or bar hopping. I also enjoy small social get togethers, but I find that even with my closest friends, I really have to psych myself up and get in the mood to go out, even though I always have a good time when I do.
I don't know if this is what you mean by being a loner. If you mean "someone who only ever wants to be completely alone" then I think that would preclude you from any kind of "amory," poly or mono. But humans are social creatures, and I don't believe any human could be completely healthy and happy without ANY social relations, so I'm going to assume this isn't your definition.
I have a hard time meeting people romantically, mostly because I don't make the effort, but also because I'm very shy around strangers.
I do not need a label to define me. Labels are sticky and I hate the glue they leave behind.