Last winter it started. When our bedroom gets warm during the winter only one of our walls smell like rotten fish. When the room is cold you don't smell it at all it never did that before until last winter of 2013 I don't know what it. It always stays cold in there even with our wood stove going but if we stick a small heater in there to warm up the bathroom before we shower thts when we smell it.

PLEASE HELP!!

Sounds like a moisture problem, since it's gone on so long. A qualified Home Inspector can give you more specifics. Most Realtors can put you in touch with one in your area.