is it possible for a pakistani official passport holder to have multi transits during 30 days

i will be going to china and then from there i have a plan to visit hong kong for few days and then again come back to china.will it be possible for me to have multi transits as i have an official pakistani passport and i am exempted from visa.
i also want to know that do i need to visit chinese embassy in islamabad before going to china or i just buy a ticket and move.what do u suggest?