My faucet will not stop leaking, what can I do?

My faucet in my bathroom is constantly dripping out water from the spout and I cannot get it to stop. I took the head off of it and inspected the rubber ring that prevents it from leaking around and its fine, I tested the handle it uses and its fine. When I push it all the way down, it leaks faster, and when I move it around to try and get it to stop it just doesn't. I tightened the head as tight as I can get it and it still drips. What can I do?