[Steveo57]

I agree with the above comment. I'd check the roof really good but if you're taking showers and living in it full time it probably is condensation. A lot of moisture from the shower and it's gotta go somewhere. It wouldn't surprise me to find the moisture getting up into the ceiling and condensing on the underside of the roof around the shower area since it's not sealed up good around that vent skylight if you have one.

I wonder if it would be wise to try to seal up the inside of the vent and skylight openings under the trim to keep the moisture from sneeking up into the ceiling area? It's similar to what we did around the AC vents in the ceiling that weren't sealed well and would let the cool air escape into the ceiling.