Replaced fuel pump now gas gauge isn't reading right what could the problem be

What is your question?

Change the fuel pump and gas gauge seem to be reading right well got down to 1/8 of a tank on gas gauge and ran out of gas put gas in gauge moved up couple days later got to a line above a quarter and ran out so went to fill it and could only put 5 gallons in so now it reads full and once it gets to between 3/4 full and half running out when put gas in now once the gas gauge reads full it won't let me add anymore gas but then acts like it out of gas between 3/4 and half and worked fine before new fuel pump was put in what could be my problem please help