Gas Gauge adjustment

Is there a way to adjust the gas gauge needle. I believe mine is not working properly. I fill my tank up and it points to the full position, I drive a couple of miles and I notice it goes up and down a lot. Sometimes it point to the 3/4 position after driving only for a few miles. The other day I noticed I had a 1/2 tank and after a 95 miles trip the tank was almost empty. I know there is no way half a tank would give me only 95 miles after a complete tune-up.