Seasonal affective disorder is a common condition. I would strongly encourage you to talk with your doctor
as there in fact many good treatments for seasonal affective disorder.
Before answering your question, it must be said that with any mood disorder we worry
about your current state of mind. If you have any thoughts of hurting yourself, committing suicide or hurting anyone else I would urge you to go to your nearest emergency room immediately.
Seasonal affective disorder (or SAD) is often a more mild experience of depressive symptoms in the winter months. The thought is that it has less to do with the cold of winter--but more with the lack of light. Therefore treatments are best targeted towards light therapy. Using bright lights during the day (really illuminating your house) even in the evening can be helpful. There is also "light therapy" with prescribed lightboxes that people can use to get the amount of light. The other therapies include melatonin which can be given at a specific time to later one's sleep/wake cycle. An important treatment can also be medicines such as SSRIs that treat other forms of depression.
Talk to your primary care doctor
. He or she can certainly help. Good Luck!