OK, for one

If you don't do any drugs, you can't possibly have it in your system. While second hand smoke may raise THC level when scanned in a lab, it's not enough to even show up for a non smoker.

Unfortunately, and this is just being blunt, you drank way too much water. It's very easy to dilute, two bottles alone could have done it. I wish you well, but I can't see anyway you didn't dilute taking in so many liquids.