Unless there is oil and water mixing, I doubt it will be the head gasket. What is the mileage?
It sounds like worn piston rings or valve seals are more likely the cause.
If its still under warranty I would take it back to the dealer and show them the failure sheet and get them to put it right.
The engine shouldn't be burning oil like that on that mileage. If its got full history it sounds iffy to me. Hopefully they will sort it without any issues.