Violet, not sure what it looks like but it does sound like your fan may be getting loose. Make sure that you fan is mouned on a fan-rated box and not just a box for a light fixture. It may came off where the box is mounted to in your ceiling. If that checks out okay you do want to check the screws that secure the blades to the motor. Make sure they are all tight. If none of those fixes solve the problem, try balancing the blades. Balancing kits are available at lighting stores.