How Long Do The Withdrawal Symptoms Of Hydromorphone Last?

Been taken hydromorphone after back surgery. I have stopped using them but have been experiencing sever headaches. Supposedly this is a side effect. But it has been going on for a week. How long do the side effects last?
Sorry can't pay nothing, I have been unemployed ever since my back went out on me a year and a half ago. Sorry to have bothered you.