A few things I have in mind. First of all, that's a lot of EQ in one week, though I don't think that what the pain is about. Maybe you're injecting it too fast. Everytime I had major pain and swollleness in the arse was from injecting it too fast. That's also a lot of gear to be injecting into one place. I agree, 3ccs is about my limit in the glutes. But yeah, what Al said, it's probably the prop in which you'll get used to, hopefully (lol).
Do what they all said, massage the spot after injecting, sit in a hot tub or perhaps take a nice hot shower afterwards.
Hope these responses make you feel better.