shower and tub run at the same time

we recently bought a house, and the bathroom tub/shower faucets both run at the same time when the midle knob is turned on the shower side. (when it's on the tub side, only the tub runs, not the shower) how would i go about fixing that?
also, the knobs are pretty hard to turn, is that an easy fix just by buying new faucets?

(we are going to a local hardware store today to buy new a new bath faucet..)

any help would be appreciated!!!

Sounds like the Diverter valve in the wall is messed up and either needs replaced, or some work on it if you can fix it without the replacing. If not able to fix, your "easy fix" may end up being a long fix due to if the valve, you will end up doing some construction work on the wall to replace, and possible plumbing work.

You gonn a fix or replace?

You need to either rebuild your diverter stem or replace it with the exact one. Post back if you need info on how to remove the old diverter stem.

we bought a plumbing book, so i think we are going to try and fix it first.