95 Fuel Gauge

On my 95 with the 4.0 my gas gauge is messed up, I think. Ever since I bought it back in November this has been going on and I hope someone has an answer for me. It has the low fuel light and it will go off when there is still 5 gallons left in the tank, the gauge also shows empty but if I go to the pump and fill up completely it will only take 14-15 gallons of fuel. It is really starting to annoy me being that as soon as that goes off there is no longer any movement in the gauge and thus no idea for me of how much fuel I really have.

I think my light comes on somewhere near the 1/8 of a tank area. My needle will continue to creep down though.

Does anyone know why this is happening or how to fix it?