Welcome to Psych Central Apugliese. Sorry to hear you are having struggles in your relationship.
You mention seasonal depression. A psychiatrist (pdoc) told me that they have sunlight like lamps or light boxes that simulate the light of sunshine.
Winter is also a time of colder weather. Space heaters or electric radiators could be used carefully keeping a 36" clearance and unplugging when not in use. Don't use extension cords except heavy duty recommended by the manufacturer.
Snuggling under the covers just to stay warm is an old eskimo trick lol.

These are easy things to change. Helping someone in depression is not easy. There are no easy fixes. To understand more you could try these links:

Psych Central - Search results for Seasonal depression

Depression - Forums at Psych Central

Keep reading and answering posts. There is also a depression chat available after 5 posts.