Brakes go way down if you press the peddle more than once

That is a common symptom of a failing master cylinder. Most of the time you can make it occur by lessening the pressure on the brake pedal but not removing your foot completely. Easing up on foot pressure, then applying it harder again allows the internal leakage to take place around the rubber lip seals, then the pedal will sink to the floor again. The same may happen if you hold steady light-to-moderate pressure on the pedal. An additional clue is you will not be losing brake fluid from the reservoir.