I have a 100 ft well... worked fine over the past year... drought came and in August water level lowered and we shut off to save pump... a lot of rain came and we measured 25 ft of water in well. However, it will build up pressure after a prime and then slowly loose pressure... can feel and hear water running through lines into tank and water coming out tank is always clean... pump will just not hold pressure and also shuts on and off right after starting even though I drain the tank... how can I tell if pump waterlogged... currently has 25 lbs pressure in air bladder

To charge your bladder tank shut the power off at the breaker and open up a cold water tap to relieve pressure. Air the tank up to 2PSI UNDER the cut in point on the control box.
As for "slowly losing pressure" it sounds like a bad check/foot valve. Good luck, Tom