From what you describe, it does sound like there is a moisture problem.
You need to identify if the moisture is coming from inside (from pipes) or outside (rain,underground spring etc).
Check outside if the gutters and downspouts are fully directing any rainwater away from you foundation slab. Make sure the landscaping is diverting water away from the house as well. How old is your roof? If you have an attic space or eaves, check for water damage. Check for flashing around windows and doors, and examine your siding for obvious water damage. If the exterior checks out, the water is probably from an interior source.
Try and trace the water supply pipes from your faucets and toilet back to the water heater/water meter. Check that the toilet is securely fastened to the floor and doesn't rock. Sometimes the wax seal between the base of the toilet and the floor fails and water trickles out under the floor.
By no means is what I've said comprehensive. I'm sure there are other places to check, but it's a start. You've come to the right place for answers though.