My periods went away for several months and then they came back. It was pretty painful, physically and emotionally. 6 months is generally the cut off point for when your periods should stop. I don't think the ER is necessary, as this very likely isn't urgent unless you are having a fever or very severe pain. But I would recommend seeing your doctor is that is possible. It will keep your health in check just in case, and it is a heck of a lot less stressful than an ER visit.