Definitely sounds like a fuel sender, but I'm bettin you still have just less half a tank when you're filling up.
Mine, a 97, had this issue in 98-99, found it became a big problem after running the truck real low on gas a few times. They replaced the fuel sender, under warranty, ever since I'm VERY reluctant to let it get below 1/4 tank.
The 2 times I have, in the last, 5-6yrs, sure enough, the gauge acts goofy. Course it was during the coldest months of the year, too. Now I always keep her above 1/2 tank, haven't had gauge issues in a long time.
I do have, though, and I don't know if other's have this problem - but I have to fill the truck on the lowest setting, if I fill it too fast, it will spit up, like a child overfed

This has been an issue for 7yrs now.