the discharge indicates infection and poor cleaning of ear.
You have not mentioned that whether it was canal wall up or down mastoidectomy
see if its canal wall down mastoidectomy it take 3- 4 months to get cavity dry and then you will not have discharge and u will have to be in constant follow up 6 monthly to ur doctor
If its canal wall up then it must have healed by now.But if its discharging then go and see ur doctor if there is perforation in the drum.
Do not clean your ears at all by yourself.