Hi, how's it going?
Its not your pump. As far as i know the car has two fuel guage senders, one is attached to the fuel pump and the other on the opposite side of the back seat. They are pretty easy to get at, see pelican parts technical articles, i would just check all connections and make sure they are both free to move.
http://www.pelicanparts.com/bmw/tech...-Fuel-Pump.htm