Make sure 1mV noise is not generated by osciloscope wires!!
If it's not, noise can come from a bad ground routing, you can put external wires from all your circuit grounds to ground of power capacitor, this can strongly reduce noise, same for VCC.
Incrementing number of stages, you will amplify the noise, not eliminated, you must put your attention in eliminating noise at first input of your circuit.
Normaly, electrek microphones has higher level of signal, maybe your microphone can be wrong.
:sm16: