What is the most likely cause of the low oil pressure warning light lighting up?

What is your question?

I think maybe there is an oil leak somewhere because every time the low oil pressure warning comes on I check the oil level with the oil dipstick and it appears not to be filled to the max. So I throw a quart of fully synthetic 5 w 30 oil in and then I'm able to drive the car for a day or so without the warning light coming on again.

What makes this problem better or worse?

Throwing a quart of oil in makes the warning light turn off

How long has your 2010 Volkswagen Passat had this problem?

for just a few days