Hey guys , I'm on a 16 week cycle of Sustanon 250 and right now Im on the 10th week,I am using 500mil a week . for this cycle I have used 2 stacks of Sust, the first gave me some good results, and the second one is been amazing but the problem is that the pain in my buttock is so bad , the first night after each shot of that 2nd stack I can barely sleep! and it continues for about 3 or 4 days until it disappears. I didn't feel that pain with the first stack. and Is not the first time I use Sustanon... What's going on?