I have well water. The water pressure gets stronger, and then gets weaker. It keeps alternating like that the whole time the water is on.

Its the pump turning on, and off.Check for any slight leak.Does the pump go to a pressur tank?

Probably a waterlogged tank. The problem is that there is very little air in the top of the tank. The system uses this air to generate pressure. When there is little to no air, the water has very little to use for pressure and so the pressure goes up and down rapidly. This causes your pump to cut on/off far too often... bad thing as it ages the pump considerably.

To check this, press the little air valve (like the one on a tire) which is more than likely at the top of your tank. Hold it for a second or two. If water comes out, then your tank is waterlogged. You can also lightly tap side of the tank with a hammer, starting at the bottom and working your way up. You will hear a tone change where the water line is. This should be about halfway up. Yours is probably near the top.

If it is indeed waterlogged, then you have a ruptured diaphragm. This calls for replacement of the tank. However, as a getby, you can turn off the breaker, open a faucet, and fill the tank with air from the valve at the top as the water escapes. Just be sure not to push the pressure too high, say over 60 or 70#. Fill the tank about half full of air. The problem with this is that the air is constantly being absorbed into the water and so, in a few months, your air will be gone again. The rubber diaphragm is there to prevent this.

Keep in touch.