Hi OP. You are not alone thinking the way you do. Most people coming to the end of a year, look back and think about things and how the year panned out.
I could be wrong, but I get the feeling that you thought this year would be different, i.e. you would have a partner, and maybe planning for children, but that didn't happen. Apologies if I am wrong about that. I am trying to be sensitive.
Nothing is really going to change that right now, unless you put yourself out there and meet someone in a similar position coming up to Christmas. Possibly unlikely, but not impossible. Depends on whether you can be bothered right now.
Otherwise I think you should be plotting and planning how things definitely WILL change for next Christmas.
Loneliness is a horrible thing, and is not discussed much. Depression far more so, but you can be lonely without being depressed.
Keep talking anyway, I hope someone will be able to help, but sometimes just getting it out helps too. X