Not 100% sure on this being an absolute requirement, but I work with a lot of instrumentation (load cells, analog inputs on industrial systems) and I ALWAYS use an amplifier to boost the millivolt signals from the load cell to something useable on the device receiving the signal. It’s not even an option.
have a look at this thread.
also, Google “Load Cell Raspberry Pi” for more threads where people are trying to do what you are also trying…