Ughhh ... I've been through this.

The first week is the worst. You will lose sleep, have nightmares, shake, and feel sick. At times you will feel like you are about to die. You will feel cold, then hot, and then shaky. This is why relapse is so common, because quitting makes you feel worse than going back on it.

Hopefully your symptoms are not this severe ... If it is, you may want to go to rehab. Even after using heroin for only several months your body goes into shock.