Intermittent Water Pressure on a Well
Have you checked the faucet shut-off valves? Aerator screens? Is there an in-line water filter? Do any of your fixtures have low-flow inserts? I would first check these things. Inconsistent pressure throughout the house at a given time makes me think you have problems beyond the pressurization system. 

Pressure gauges and pressure switches both are mechanical devices prone to failure. If you notice an inconsistency between the pressure you see at an outlet and what the gauge says, you have a suspect gauge. If you have a secondary pump (one that pressurizes the tank from outside the well) then it's easy to see if the pump comes on at a consistent pressure on the gauge, but also consistent at a faucet. If not consistent, then the pressure switch is suspect. If the pump won't keep up with normal demand then the pump or motor is suspect. If your tank is pressurized from a submersible pump suspended in your well, it becomes more difficult to diagnose and much more expensive. Lastly, don't be afraid to contact a well company.