Pump/Tank problem PLEASE help
My water pump went out a week ago, and I had an old one out in the barn, so I hooked it up. After I hooked up the pump, I noticed that my pressure tank was leaking, so I bought a new pressure tank. When I first hooked everything back up, I had great water pressure, everything was running smooth, for about 30 minutes anyway. After I took a shower, I noticed I barely had any water coming out of my faucet and the pump was running non-stop. I shook the pipe down in the well, and it built back up prime and shut off. Now, I can get the pump to prime, and to hold prime as long as I do not turn on any water. When I turn on the water,it comes out good until the water level in the pump goes down, then the water just trickles out. The pump will not shut back off unless I turn off the water and shake the pipe that goes down into the well. The plate on my well says the well is 40 feet. I measured the water level in the well, it is 12 feet deep, and my foot valve is 5 feet off of the bottom, and down about 7 feet past the top of the water. Any ideas here? I havent had water in a week, and I, nor anyone I have talked to has any idea what could be going on.