brake problem

[d3310n]

was on the highway earlier and had brake failure, didnt crash but was very close. made it home and i am very low on brake fluid. pedal makes a noise when initially pushed like moving a heavy chair on tile. pedal goes all the way to floor with very little braking force. was in an accident recently and had it repaired, brakes felt like they were freshly bled when i got it back, this was a week ago. dont think its open bleeder screw because that would have instantly caused problems. brake booster should be fine because it holds vacum whitch i can feel when i start the motor.

master cyl? or stressed brake lines from accident finally went out? drums also feel ever so slightly out of round, so ill machine them soon, and sometimes under hard braking i could feel a strange few "pops" in the pedal. its under warranty from the body shop so i dont think ill have to fix it myself, but i want to diagnose it.