Aaah yeah, that changes things a bit. Lots of people are affected by the seasons that way; pretty much all Norwegians are like that lol. Depressed and moody in the winter, and going crazy and ripping our clothes off in the summer.
I don't know where you live, but if you live somewhere where there isn't any sunlight in the winter (or max 2-3 hours per day), it's pretty normal. Annoying, painful and self-destructive, yes, but more common that you think.

It COULD also be that you are bipolar, but triggered by the seasons. Either way, I suggest you get one of those lamps that simulate natural sunlight - they're very effective when it comes to winter depression. Go buy one! I think tanning beds have some of the same effect as well, I'm not sure.
Pretty much everyone here has one of those lamps, that's how much the lack of sunlight in the winter affects us. I never see daylight anyway, so I'm not affected lol.
They are somewhat expensive though, but worth it.

I think it's important that you start fighting this depression asap, and don't just give up and let the depression take over. Try exercising, and also eating a lot of chocolate. Just don't eat so much that you gain weight; but chocolate releases endorphine - which makes us happy, yay! And take care of your body; take your vitamins, reduce junk/unhealthy food, don't stress etc. And make sure that your surroundings are clean and tidy.
Yeah, all those things actually do help somewhat - but they're hard to do if you're depressed... except the eating chocolate bit maybe.

I hope it won't take too long before you get a psychiatrist, your regular doctor should be able to prescribe antidepressives if there's a need for it - but if you're bipolar you should be a bit careful we those; they can make us go a bit... crazy. Plus your doctor sounds like a jerk.