1999 Dodge Avenger Engine noise

My engine makes a tapping noise that I think is coming from the valves cover. The tapping noise starts and stops. When the engine first started tamping it only made the noise when the engine was extremely cold in the winter, then it started happening all the time.
Also I noticed that while idling the oil pressure gage reads low although it goes to normal while driving down the road until I stop then it fall to what I think is low. The oil light has never gone on.