sounds like a stall to me also.with flaps at full down they create alot of drag and you should still have about 1/4 to 1/2 throttle on the engine depending on size and prop.once over the threshold you cut the power and let it settle down and flair slowwly a few inches above the ground.sounds like you recovered from the stall twice and on the third time by adding elevator before the speed increased it stalled and snapped on you.any time a wing starts to drop or the nose drops during a landing approach it is an early sign of a stall.nose down then add power slowly then ease in elevator.