I hear water dripping behind the wall where the bathroom sink is located and my master bedroom carpet is wet along that wall. What could be the problem.

Sounds like a leak to me! Immediately, shut off your water main (at water meter or pump), or if you don't know where the main shut off is, get some help from a neighbor or call a plumber to find the main shutoff and stop the dripping sound (LEAK? )!

Once you have to stopped the leak, work with the local plumber (or friend) to help isolate the problem and repair it. Post back as you need... glad to walk through options as concerns arise, OK?

Mark