I found that my submersible well pump has been running nonstop for several weeks( power bill through the roof). It will not pump over 50 psi. I turned the cut out pressure down to 40 psi it works fine now.It was 40--60. But the cut in is now 20 psi and the water in the house goes up and down. I turned the valve out of the tank off but can not get over 50 psi. I think my pump is going bad.It has a new pressure switch 4 mo. Ago.
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Sounds like the pump, but it could also be a leak in the well pipe that leaks enough water to keep pressure under 50#. How far down is it?

I don't know. I bought the house 5 years ago and have no info on the well. The pump is 115 volt so I believe it is 1/2 hp and most likely not to deep. But I don't know unless I pull the pump.

When the pump shuts off it doesn't loose pressure until water is used in the house.

"When the pump shuts off it doesn't loose pressure until water is used in the house."
That would seem to rule out the leaking pipe idea, although a check valve at the top of the well pipe could still "hide" that issue. Unless you want to attempt an adventure (pulling up the well pipe and pump), probably time to call in a well pro.