Why are my earrings hurting me?

I got my ears pierced 3 months ago and until a couple of weeks ago wern't hurting me at all. recently, a lot of crust has been building round the hole which made it hard to take out earrings. I've been wearing sterling silver earrings most of the time, i've worn non silver ones a bit, they didnt hurt much. recently, the sterling silver earrings im wearing are really hurting and I cant twist them without them hurting, and theres a lot of crust in the hole. Just in case it makes a diffference, I havent worn any dangly earrings.