My 03 altima (alot of miles, I do a lot of driving)is disolving oil quick. I get regular oil changes. I had oil put in Thursday by Friday engine oil light was flashing again. It's slowly (stalls)cranking but it starts every time. I had it check by two mechanic who say there is no leak, but they can't tell where the oil is going.. I have to get fix can't afford to buy another car. My ? Is y am I losing oil so quickly/what could b the problem?

If you have no leak externally, then it could go out the exhaust(rings/valves)or mix with the coolant.
Maybe do a Compression Test