Oil pressure

my oil pressure gauge seems to be a bit low. when i first fire up the engine, it will read about 40psi but as the engine warms up it goes well below 40(at idle) and when revving or accelerating it will increase. I have no drivability problems whatsoever and the oil is completely topped off and changed every 2k miles. It has been like this for a while but i was just wondering if it is possible that hte oil pump is overheating when the car gets warm and not pressurizing properly? Or do i just have a bad pressure sensor. I have replaced the pcv recently and everything seems to run fine, but im just a little nervous about the pressure becuase when flipping though hte manual the other day it said that the v6 should run at 60 psi

also, my car does have a "check oil" dummy light which has never come on, dunno if that would mean anything?