I have replaced the washers in the bathtub faucets... twice... and they still leak! What can the problem be and how do I fix it? Please help!

Sounds like your faucet seats may be bad. Shut the water off and pull the stem and washer assemblies. Take your finge4r nail and check the seats that the washers close against. If they are nicked or rough they must be replaced or they'll just continue to eat up washers. Good luck, Tom