Wasting to much gas and when top the gas tank it doesnt mark full tank.

What is your question?

Other day I filled up the gas tank all the way till it topped off. When I was driving the fuel gauge was marking it going down to fast like it was wasting to much gas. Then when I tuned the engine off it marked low so, when I was driving the gauge started going up slowly. I would like to know what's the problem.

What makes this problem better or worse?

When it's cold or hot

How long has your 2005 GMC Yukon had this problem?

Just about a week