I had the same problem once and it was the pee trap under the shower pan. It was broken. If you have access there check. A water line break is usually something that runs all the time or certainly is under pressure, intermittent can be a drain problem only occuring when you shower.
Also water finds strange places to flow so where the water is exiting can be far removed from where it is leaking. It took a process of elimination to find my leak because facually it seemed most likely to be the washer dryer---not so it was completly on the other side of the MH.
Good luck, yu should be able to find this and usually when you do it is an easy inexpensive fix. No sense having a $110. per hour tech "looking around" for an hour or two.
I do all my own stunts
03 Dolphin LX 6355, Workhorse W22, 8.1 vortec, 04 CR-V, Blue Ox, Brake Pro----Norm, Barb and
Doc(He's a PhD)