Stop resetting your ECU...
The system is running lean, the ECU is telling you this. When you reset the ECU, you're making it run EVEN LEANER. You're also wiping out ALL evidence of the problem, so that nobody can do a thing to help you.
That said - if the car runs fine after a reset, and gets steadily worse up to a system too lean CEL, AND you hear an exhaust leak under the car, this could be one of the rare circumstances in which resetting the ECU is not a horrible move. You probably have a pre-O2 exhaust leak which is feeding fresh air into your exhaust system, causing the O2 to read lean, and causing the ECU to dump in fuel to "correct" for the problem. Your gas mileage has probably gone to **** as well. You need to find/fix that leap ASAP or you could end up washing out your cylinders.