An electrical submersible well pump assembly having a progressing cavity pump, a pump motor, a flex shaft connecting the pump motor to the pump, and a gas/liquid separator on the inlet to the pump. An inner and outer housing circumscribe a portion of the flex shaft, each having fluid inlets. The fluid inlets on the outer housing are above the inner housing inlets and an annulus is formed between the inner and outer housing. Wellbore fluid enters the assembly through the outer housing inlets, flows downward through the annulus, and into the inner housing inlets. Gas separates from the liquid as the fluid flows downward from the outer housing inlets to the inner housing inlets.