Toilets, Sinks, Showers, Tubs and Disposals - Shower Leak: What next?

I have a 2 story home. Two years ago, the ceiling below the upstairs shower starting showing water spots. The spots grew worse and I used some rubber-type caulk around the edge of the upstairs shower where I thought it might be leaking. I cut out and reapaired the ceiling downstairs and installed a water efficient shower head to reduce the amount of water coming out of the head....it actually "feels" better with the new head.

Two years later the water spots are back. Someone said I might need to replace the shower pan. I have a tiled shower. Is there some other possible solution? Did I try to fix the wrong problem? I searched these forums and it looks like a major and expensive task to basically tear out and replace the entire shower.

If I have to hire an expert...what kind of person am I searching for? A plummer, a tile expert, maybe both?

Also, I found out my neighbor has the exact same problem....and we had the same builder. The homes were built around 20 years ago.

I think I would recut the ceiling first to find the cause of the leak. It may be the drain flange, or pipe leaking. Lot easier to fix than the tile tear-out. Good luck.