heroin withdrawals; how long do they last?

My Nephew moved with me from Chicago, He had been doing drugs for many years. He decided to quit, but this has been the second time i have to take him to the E.R. due to super fast palpitations, pain in his chest, difficulty to breathe... They always ask him "do you use drugs?" his answer is always no! because he is not using them right now. I have talked to several people who claim that "his symptoms" (vomitting, sweats, heart palpitations, etc) are "normal". How long do i expect this to keep on going, the last time I took him to the E.R. was less than 3 weeks ago! Is this a sign that he is still doing something?

Im sitting in bed reading this and realizing that I have the same symptoms. I am in my fourth day of herione withdrawal. I, of course, am not a doctor. But it seems like your nephew has recently used drugs, and is now in the withdrawal proccess.