The water flow from my pump slows to almost nothing after 5 or 10 minutes. I change the filter and it has a great flow for a few minutes then slows to a trickle.

I have sort of the same problem...sort of. Intex 14x48 pool with pump upgrade. When I turned the pump on it sounded sick. I thought I had cavitation but checked all my lines. No leaks. Took the pump off the system and checked it with a dry run. Impeller sounded and appeared to be impeded. Opened everything up and couldn't find anything impeding the impeller operation. Put it back together and turned it on...then I heard the familiar hummmmmmm of a working, unrestricted impeller. Put the pump back in line with the system, primed the pump and started her up...hmmmmmm, giggle, girgle, girlie...same old thing. I can't figure it out. Thinking of just buying another one.

There are screens at the hose connections to the pump and at the inside pool outlets and inlets. Check to make sure their clear. Also be sure your using a New filter not one you have cleaned off.