WHAT is that smell?!?

I was sitting on my couch last night, (which isn't so much a couch as a futon that folds down into a bed, but is functional enough to serve as a couch) when every time I leaned forward, I smelled something awful. I know it wasn't me that the smell was emanating from, so I kept asking DH if he had farted.

"No hun, it wasn't me. I don't smell anything. I think you're crazy."

This is a typical phrase during my pregnancy. Smells that I think are there, are usually not. Tastes that I think I taste, are usually in my head. Very occasionally, I'm proven right though. Tonight was one of those times.

After 2 hours or so of continually smelling this terrible scent, I finally got down on the floor on my hands and knees and sniffed the couch in different areas. Finally, I came to a spot that made me nearly wretch.

"There! Smell RIGHT THERE!" I gestured wildly to the noxious spot with a mixture of triumph and disgust. DH leaned forward and put his nose right into the spot I pointed to and almost gagged himself.

"Ok, yeah, I smell it too."

Now the question became, "What the hell IS that smell??" We turned on the lamp and checked the spot for cat poop, on the off-chance one of them had tracked some onto the couch (which never happens). Nothing.

"I guess we should wash the cover," says DH as I lift up the sheet we have covering the futon mattress. Another sniff of the same spot reveals that no, it wasn't just the cover. He smells it again too. So we lift up the second sheet underneath, and I proceed to sniff the mattress itself. I recoil in disgust and say, "Apparently it's the mattress!!"

So what does DH do? He takes the sheets off and lays down a thick blanket to try to mask the smell.

I have no idea how we'll get that smell out, or where it came from, but my question is this:

WHY does my couch smell like poop, when there's no poop to be found?! Argh. I suppose I shall have to get used to strange smells once Marshall arrives. What better time to start then now? *sigh*