Well if we begin with theory that gun shots and cricket bat noises can be confused, then there's no reason that noises had to be consecutive.
We also can deduce that if OP's story is true, witnesses might have been awakened by gunshot noise, but would not have consciously heard it.
If OP accidentally shot Reeva with first shot, then spent several minutes trying to deal with the situation of her being shot and not being able to get in the toilet area, it might fit the evidence.
Shot 1 - hits Reeva's hip
Shot 2 - misses
OP tries to get into bathroom to save Reeva, shouts for help
Cricket bat breaks a door piece out
Reeva is freaking out, says she'll call police
OP panics because she won't stop screaming
Shot 3 - hits Reeva's arm
Shot 4 - hits Reeva's head
Could this fit the evidence, or approximation of the evidence?