Losing coolant but do not know where.

[Madmoly340]

I thought if it was the head gasket you could tell by looking at the oil and white smome pouring out of the stack i have neither issue.
I am having some issues with my air system. And I know there is nothing wrong with my ... you did it about 6 months ago and the truck is running perfect except for the coolant.
If by chance it is the head gasket how long can I wait to have it fixed because I need to put some loot together to give to your guys over there in GA. They are the only ones I will let work on my truck.
Thanks
MIKE