Need help on what this could be. A few days ago I turned my car off with my foot on the brake and the pedal pressurized enough to actually lift my foot up... and in like 2 seconds! Now it does it every time I turn off the car with the brake pedal in. Then the brakes have felt weird like there is little pressure while I'm driving (which worries me). Then to top it all off, now when I push my brake pedal down all the way, I can hear a loud hissing from the dash area (either pedal, or slave or master cylinder.

I'm soooooooo fed up with this car right now that I just left it in gear to be sure it doesn't roll and walked away from it when I got home, so please help me get the car right so I can sell it!