Does anyone know or maybe care to explain what might be causing my gas gauge to fluctuate an entire half tank at some points during travel? it also seems like my fuel economy has gone to shit since this started happening too.

I've never had this problem before so its def not normal and the amount of fluctuation is way more than it should be. i can never tell how much gas i really have anymore. i assume something in the tank end of it is broken but i figured id see if someone had this same problem and how easy it is to fix. thanks for anything

'95 civic dx coupe.