My water well constantly cycles on and off. Pressure goes up then down.

If this happens only while water is being used, then you have a waterlogged tank. Press the little tire valve on top of the tank for a few seconds. If water comes out, then you have found the problem.

If this happens when water is NOT being used, then you have a leak somewhere, probably in a checkvalve.

BTW, is your pump in the well or above ground?