While the Gas plumber is trying to find the leak I would suggest that every time you finish cooking "If you have a Gas Cooktop" & Showering if you have instant Gas hot water to turn the Gas supply off at the Gas meter. It is also safer.
This way you will not continue to clock up a high gas bill.
If you have a Gas Hot water tank it would be best to talk to your Gas plumber in regards to keeping that heated.
One of the AGL team here in the Neighbourhood should get back to you Monday onwards.