Brake pedal goes to the ground b

I almost got in an accident backing out of my driveway the other day. For some reason my brake pedal went to the floor and didn't stop. Thankfully I used my ebrake! But today I replaced all my brake pads, replaced a leaky rear passenger caliper, bleed all 4 brakes. And still couldn't get pressure to build up on my brake. It would feel ok for a second or two but with constant pressure it goes all the way to the floor with no normal feeling. It just goes from spongy to a deflated pedal going to the floor. Would this be a master cylinder issue or the brake booster? Or neither? Please help. I'v recently got laid off due to company downsizing and I need my car to find a new job! Thank you all very much.