Any change drastic change in your cycles, especially when they stop, can be very distressing. If a women has normal cycles and they suddenly stop, its known as secondary amenorrhea. It can only be diagnosed after a women has had no cycles for at least 3 months. You can present the problem to your primary care physician
who can order a variety of blood tests if he or she can't figure it out through history and physical alone. By far, the most common cause of secondary amenorrhea is pregnancy. The test you took was negative, but I would repeat it to be sure. A second common cause of secondary amenorrhea is weight loss
. If you have been aggressively dieting lately, or engaging in a rigorous exercise plan, your periods can stop. If you think this describes you, then I would see your doctor
very very soon to get evaluated. Other causes of secondary amenorrhea include thyroid problems and secretion of prolactin. These are endocrine conditions can be diagnosed through blood tests. Finally, pre-mature menopause does occur, but only after all the other causes are ruled out. If it has been close to 3 months since your last period, don't wait any longer to be seen. Either your primary care physician or you OBGYN would be good choices to evaluate your problem. Good luck.