are you flying wood props, or plastic/nylon if your flying wood, then stop, then try master airscrew props until you can land without a prop strike, the MAS props can take a beating and will last for a while then after you have mastered landing without stopping the engine on the prop, swithch to wood or fiberfill props like APC, the APC will snap off as well if you hit the ground hard enough with them.

its hard to garentee that the prop will stop on the compression stroke if you kill the engine, it helps but not all the time