I discovered a water stain on the ceiling ABOVE the toilet which gets bigger and wetter when I shower. This master bath is below an upstairs closet, which is not wet anywhere and only contains clothing.

This happens regardless of whether it is raining outside. I really think it has something to do with the shower.

Please help!

If the ceiling has been repeated wet it needs to be opened and replaced anyway, this will let you see if there are any pipes up there that are leaking. Mold starts to grow in 24 hours after repeated wetness so don't wait too long on this project.

I'd betcha a brand new dollar bill your vent came disconnected or otherwise unsealed from the connection that vents to the outside of the house. As the steam from the shower condensates in the duct, it leaks out and it pools onto the sheetrock above the toilet and that is why your ceiling gets wetter with each shower.

Instead of sending me the dollar, hand it off to toys for tots or habitat for humanity or whatever interests you, even if it's a new song on itunes. :)