ENGINE KNOCKING I NEED YOUR HELP PLEASE!

I have a 94 Lincoln Town Car its has roughly 135000 miles on it it ran great until I let it sit a month then I noticed it had no oil so I put 3 quarts in it and went to work and back about 28 miles round trip by the time I got home my oil light was on and it had this terrible knocking noise so I put more oil in it which was 10w 30 I believe and that knocking is still there it sounds as if its coming from the passenger side in the front of the engine near the spark plugs when I press the gas it gets louder and louder when I got on the ground I noticed I had an oil leak also but not in the normal spot its leaking from around the middle of the car underneath not up by the oil pan but further back does anyone know what this could be or what I could do to quite the knocking thanks for anyhelp