Gas gauge

Hi car pros. Im having a little problem with my gas gauge.I just replaced my fuel pump for the second in a month but anyway when I replaced my first full pump the gas gauge read a quarter of a tank when it was full. And sence I put this last pump in it stays on E with the gas light on, and the car is almost full of gas. The last time I noticed when I dropped the tank the floater arm feel off some how it was at the bottom of the tank. Do you think this could have happen again? If so y does it keep falling off now? The arm just slides in a little hole. What do you think my problem is? Thanks.