Brake pedal goes to the floor?

The brake pedal goes all the way to the floor but comes back up and when you reapply it, it gives a little pressure for the brakes to stop. But, if you do it again it might give you a little more pressure but when you apply then there's brakes and then there's not. The pedal is not high, it's not hard, and the engine does not stall or shut off. Do you have any ideas why my pedal goes all the way to the floor? It doesn't fall to the floor there's very little pressure, and if you pump it again there's a little more and if you pump it again there might be none and there might be some, then they might be like regular, but the next pump it's all the way to the floor. The car keeps moving, it does not stop! That really sucked today! LoL whew
I'm really confused by everything that I've read. Do you think it would be a vacuum leak somewhere? There's no lost fluid either. Thank you so much for anything!