Food scales

Sorry if this has been answered already.. I finally bought a food scale i lost 7lbs b4 xmas n havent lost a pound since ive 10lbs left to pre pregnancy weight i kept reading when u get closer to your goal u have to tighten up logging.. So im just wondering how do u manage to weight n log properly for example im cooking a beef stew for dinner just a bit confused as how do a weight it?? do i do it before its cooked or after because if i weight all da ingredients before i cook it how do i no how much is in a portion this is more confusing than what i thought.. t.i.a...