I loosened the PRV.It decreased inside water flow and the gauge still is 100 psi.I tightened it back so I could get the inside back to normal.
What should I do?

If adjusting the PRV does not change the reading on the pressure gage then replace the gage. It's faulty.
The average house pressure should read 45 PSI with the very top end at 80PSI.
Let's be sure how to adjust your PRV.
1. Close the gate valves before and after the PRV. Open
The bypass valve slowly in the bypass line and blow
The system down. Care should be taken not to open
The bypass completely to prevent the safety relief
Valve (if installed) from popping off. After blowing down
The system, close the bypass valve.
2. Loosen the lock nut on the adjusting screw to allow
Adjustment. Relieve the adjusting spring. See Figure
2-1.
3. Slowly open the inlet side gate valve to the fully open
Position, and partially open the outlet valve so only a
Small amount of fluid can pass.
This bulletin should be used by experienced personnel as a guide to the installation of the Model GD-24 Pressure
Reducing Valve. Selection or installation of equipment should always be accompanied by competent technical
Assistance. You are encouraged to contact Armstrong International, Inc. or its local sales representative for additional
Information.
1. An Armstrong ìYî strainer (20 ñ 100 mesh, depending
On liquid quality) should be installed before the PRV
To reduce the chance of dirt fouling.
2. Pressure gauges should be installed before and after
The PRV.
3. Piping a bypass line with a globe valve around the
PRV will allow system operation while the PRV is
Being serviced. Install only if fluid cannot be shut-off
To service PRV.
4. Do not install quick opening or closing valves
Downstream of PRV.
5. Install the PRV with the flow in the direction of the
Arrow on the body.
Improper adjustment of the pressure reducing valve may cause hunting, improper control, and possible damage to the
Valve itself. Adjust the valve as follows:
4. Slowly turn the adjusting screw clockwise until the
Desired pressure is obtained on the downstream
Pressure gauge.
5. Slowly open the outlet valve to the fully open position.
6. Adjust pressure again after system stabilizes.
Turning the adjusting screw; Clockwise increases
Pressure and Counterclockwise decreases pressure.
7. Tighten the adjusting screw lock nut after adjustme

Let me know if this helps. Good luck Tom

Thanks for your quick/detailed response.
I just bought a Pressure Gauge last week,so I doubt it's faulty,but your detailed instructions makes me want to get a professional,rather than me risking making it worse.I've had a couple of plumbers tell me,for years,my pressure is too high,so I better take care of this now.