the funk

So I'm driving to work today and about 30min into my drive the air in my car starts to smell. I dont think anything of it until it happens on my way back home. I picked up a mate and he thought it smelt like BO. Well it wasn't either of us smelling up the car, and after a bit of driving it doesn't go away.

So i try turning the a/c on and that kinda helps for a bit but then the smell starts coming through just like before. Now remember i have climate control so for the most part its set @ 22c and its untouched for months at a time.

We pull over and pop the hood, but there is no smell coming from the engine and everything appears normal. Get back in the car adn we can really smell it now having been outside the car for a moment.

My first thought is I have mold in my air system, or a bad airfilter. Have any of you had this problem on your cars? Any ideas of what this could be?