crank no start engine slowly clicks loudly

Well i went to pick my sister up from school, i was early so i shut off my car to wait.. i tried to turn it on shortly after and it sounded like a pin flew off something (as it was starting up) and then it was like a woub woub woub sound like a cartoon as it died.. i went to start it again and the crank shaft was spinning but it gave a loud click click click slowly as my engine was cranking.. please if anyone can help me you'd save me from my depression :(... thanks