There are some basic and stress-free tests you can do, as a homeowner, to narrow down what type of leak you may have.
Checking your water meter
If you have the ability to do so, check your water meter over an hour period without interruption or the use of any water. If, after this duration, there is no change to your water meter the shower leak may not be pressurised by your water pipes. It may be leaking due to waterproofing or a waste pipe issue.
Checking your taps for any water leaks
Check your tapware, shower head, hoses, and hand pieces for any visible leaks, drips, or abnormally loose-feeling fixtures. If in doubt, call your trusted plumber.
Stop using the shower for 24 hours
If you can use an alternative shower in a separate area of the house that you don’t suspect to be leaking, use this instead and let the leaking shower/wet area/bathroom sit unattended for 24 hours. If things appear to start drying up then the leakage may be from waste pipes or waterproofing.
If things stay wet the leakage ay be pressurised from the hot or cold water supplies.