Oil Pressure problems

Sounds typical of worn engine bearings and at the mileage you listed, that's to be expected. Start by measuring the oil pressure with a mechanical gauge so you don't overlook a defective pressure sending unit. If the pressure really is low, I'd drop a new set of crankshaft and connecting rod bearings in before any real damage occurs. The pump could be worn too but I'd suspect the bearings first, especially if the pressure is higher when the engine is still cold and the oil is thicker.