Feels like iM not getting to get my wheels to drive forward

OK WELL, MY CAR WILL GO INTO GEAR, WHICH IS GOOD. WHEN I START TO TRY TO DRIVE AND I STEP ON THE GAS MY ENEGINE JUST REVES UP TO ABOUT 4000 RPM'S. THEN IT WILL SLOWING START TO MOVE. IT DOES THIS THROW ALL OF THE GEARS, ALSO DOING THIS WHEN I GO BACKWARD AS WELL. WHAT MIGHT BE THE PROBLEM?OH THE BACKEND WILL ALSO SHAKE A BIT, WHEN THIS IS GOING ON.