Dear Duran: What you're describing is exactly what happened to a friend of mine 2 weeks ago. A musty, moldy, and unpleasant odor coming from the sink area but specifically behind the fridge (next to the sink). We discovered after the process of elimination that the fridge waterline poly tube ( perhaps yours is copper) that provides water to the icemaker and/or waterdispenser was leaking and eventually rotted the drywall behind it. You may want to check your trash disposal, if you have one. Or check your water connections under your sink. Sometimes shut off valves and flare nuts need to be replaced after manipulation. Good luck!