The check engine light has been on since I got the car

What is your question?

when plunged in it says a code has an evap leak I've been to several shops and no leak is found short of examining the gas tank. I was told not to worry because the car is. Not running badly at all so how do I know when something is. Really wrongs of the check engine light stays on? Any suggestions I've changed the fuel cap and spent 329 trying to get the leak none found!!! I forget the code # but it's evap leak every time it's diagnosis.