I don't have any hot water in the shower/tub. Everywhere else is fine and the pressure is really low on the hot side.

Shut the water off under the cabinet ands open up the faucet. Remove the cartridge and check and clean the hot water inlet port. While the valve's open place a pan over it and turn the hot water on to flush out the supply. You should have a full sream when you do this. If not let me know. Good luck, Tom

Tom Lisalegs talking about shower/Tub not sink.

Lisalegs , shut the water to house remove the cartridge from your shower/Tub valve now ask some one to turn on the water for as few seconds to flush out any debris from the valve, shut the water install the cartridge and check see if you have good flow if not change the cartridge, please tell us the name and the brand of your valve, Thanks.

John