brakes stop and continue to go to the floor. what is the problem? on 2008 Scion xD

Brakes catch and stop but continue slowly to the floor,if I would be too long at a light I felt I would begin to move. Don't seem to pump up easily either. What is wrong.

Asked by for the 2008 Scion xD
Master cylinder most likely suspect. Have it checked out ASAP!! And be careful.