dared1

I have an expedition with approx 193K miles on it. I religiuosly change the oil as scheduled. The vehicle sat for about 10 days and while driving I turned a curb and the oil light came on and I heard knocking noises. Tried to make it home but car shut down. I let it sit for a couple of hours, check the oil and it wwas very low (last oil change 1/10) Put 2 quarts in and a turned on no problem and sounded fine. Drove her home which was basically around the corner. Later that day went out truck and and turned it on and added 2 more quarts of oil and let car on for a while...then the light comes on again and I hear the knocking noise....no oil on the ground nor do I smell oil burning. Turn car off then back on, car sounds fine...5 minutes later the oil light on and the noise. What could it be that is throwing my oil pressure off?