Since the problem is recent I would suspect a faulty pump or a blockage in the pick-up,smashed pan? 1st I would just change the pump,then if still occurs would check pick-up in pan, then lifters,more than likely a new pump will eliminate most of the problem,ran into this a couple times with 440's and a 318 or two,very frustrating,but pumps are cheap,while its apart check oil pump drive gear for wear or breakage and replace if necessary. with the pump off you could blow thru pick up to remove any obstruction, remove oil plug in pan and force with air some kerosene/diesal/solvant down pick up tube to help remove derbis or build up on/in pick up, just make sure to drain it all very well before you add new oil, I have done all this in the past with no problems,as a last resort you could drop the pan and inspect...