What model trailer do you have? Water can travel quite a ways before showing up at a place you can see it. The shower mite not be the culprit. Hard to tell unless you can get allot of light in the underbelly and look at everything. Is the shower p-trap a glue or knuckle joint? If knuckle joint, nut might be loose. Many possibilities.
Dave, Cha & Nate
2011 Toyota Tundra Crew Max 4wd
TST 507 TPMS, Butch's Latch