Not really. If you think about it folks should be happy with family all year, not just christmas. It's probably getting you known more as media and shops go all in our faces about it with their advertising. 

And yeah, the cold, shorter days do effect the ability of some to bounce themselves out of a depressive mood, even if its a mild one.

No, your not a minority. Many people feel this way around the Holidays. Feel free to message me if you need to talk about it.

Oh and I'm not sure if it would help, but I recently wrote a fic about a pretty similar situation, if you feel like reading it. http://www.fimfiction.net/story/150990/the-meaning-of-hearths-warming

Have a merry Christmas =)