Please tell me what would cause my water pressure for hot water be very weak and the cold water pressure is normal.

Attach a hose to the drain on the water heater and open the drain... how is the pressure? Does it start strong and then weaken? If so, then something to do with the cold water supply into the water heater is causing your hot water issue (shut off valve or the cold water nipple). If flow out the hose stays strong then the issue is at the hot water nipple out of the heater, a shut off after the hot water nipple, or it could even be your pipes (if old and galvanized).

Start there...

Mark