600mg Test E is a solid and basic cycle.
There should be very little sides to worry about.., If you are runninh an AI and HCG?
The pain is just your bodies reaction to a needle and oil going in to the injection sites; especially if they are new injection areas..
I still get PIP from 1ml Test E every nown and then, nothing to worry about unless it becomes obviously very red and swollen... But again very rare... Could also be you are injecting too quickly/not deep enough and the oil sits between the skin and fat which can cause redness and irritation but should go within a week...
I hate to break it to you but you are way above 10% Bf mate... Nearer 20... Just being real with ya,