Having trouble with fuel gauge reading amount of gas in tank!

I'm having problems with fuel gauge, it's not reading amount of gas i have in my tank. I had my fuel pump replaced due to the fact that i did'nt pass smog check (lean fuel) and ever since the fuel gauge indicates i have half a tank of gas, which is incorrect cause it wont go down. Got stranded once without gas so i got screwed. Any help will be greatly appreciated and a thanks in advance.