my car shakes back and forth real bad when I press the breaks what can it be?

Your discription is vague, vacuum assist brake booster may have a leak, or the vacuum hose leading to it. It can also mean your rotors are out of round, but this will not give you a feeling that the vehicle is about to stall.

Typically when a car shakes real bad when pressing brakes it is caused by the brake rotors being badly warped. The "feeling like it is gonna die" part throws a little wrench into this theory, but I would start with a good brake inspection.