2002 Audi A4 Low oil light is on

My 2002 Audi A4 1.8T quattro has had a problem with the oil light in the past. This time I was driving and the low oil light came on, so I immediately got off the road and turned it off. I let it cool for a minute and then checked my oil, it was really low. So, I put some oil in it and checked the dipstick and it was in the right spot. I proceeded to drive and the light had gone off. Then about 25 miles down the road the Low Oil light came on again. Once again I immediately turned it off and waited a few minutes and checked the oil level, it was perfect. This happened to me before, but I kept driving and ended up having to replace my engine! So this time I refused to drive anywhere and am having it towed to my a place near by. When I turned the car off it was running perfectly normal. I have a feeling the reason this is happening is because there is sludge in the engine, and as a result is starting to clog up my oil pump, however, my engine is still running normally. Now my question is what should I do? Do you think Im right and if so then how much money do you think it would cost to fix it if the oil pump is bad? Would flushing the engine of the oil and dropping the oil pan and everything work? Please help!