Right front break caliper jamming?

when i apply my breaks it starts shaking and i can hear rattling from my right front break caliper, like my car starts shaking, and then it stops, but when i hit the gas it gets stuck again like its jammed and i cant move and its hard to stop,i had to e brake it all the way home ive changed my break pads not too long ago, any suggestions? i also drive 99 9-5 saab wagon,