Tori, did you just notice this smell or has it been there for a long time? Could it be a musty smell from somewhere? Or a sewer smell coming out of one of your drains? Is it all over the house, or does it just seem to be coming from one room. If you can't tell, try keeping the doors to each room closed all night and walking into each, sniffing to see if the odor is stronger one room than another.
A friend of mine got divorced years ago and was awarded their house. She started noticing a smell and couldn't figure it out, but it seemed to get worse and worse. A group of friends all went over and started our sniffing--could you imagine our surprise when we found shrimp in her floor heating ducts? And, not just a few, the sucker must have spent a fortune buying them. Needless to say, she got even.
