Sprinkler Pump Driving me nuts!

I prime my pump and get it going with the sprinklers on but there is not that much pressure coming. Had it going well last summer with more pressure. Now i have three zones and when i shut one zone off the pressure to the other zones dies and soon there is no water coming out at all. Please somebody help me before my lawn dies. Thanks

It sounds like the pump may be cavitating, where is it pulling water from

its pulling water from a well, what does cavitating mean?

You say you have three zones and when you shut off one zone the other two run out of water. It should be the other way around.

What happens when you just run one zone at a time?