The situation that you have described points towards the need for formal assessment of the child.Also we need to understand that children learn through observing others.The symptoms such a repeating something again and again point towards some neurological issues that a child might be experiencing.
Hitting the child will relieve you of your frustration but at the same time make the child aversive to you and would be very negative for the relationship in long run.Please see a child Psychologist immediately.
Next Steps
You can get in touch with me ,we can do a proper assessment of the child and work out the future course of action.
Health Tips
learn some anger management for yourself, do not let your anger and frustration affect the child.
accept that your child is unique ,focus on his positives ,enhance them and wherever there are shortcomings, seek professional help