I am fairly new to plumbing repair. I don't know all of the exact terms, so I'll try to describe it well. My tub shower has one knob. It's your basic- turn left to turn on and the farther you turn it the hotter the water gets. Between the knob and the spigot there is a stem that you push in to turn on the shower. Here's the problem: When we turn on the water, the water is spraying from the shower head- AND it's spraying out of the stem/button. The stem/button has been released (it's not pushed in even though water is coming out of the shower head). It started this all of a sudden. With the water off, I have made sure the button is released. Water will not come out of the spigot, just the shower head and the stem (where I've never had water come out before). Can anyone walk me through what to do? Thanks!