Any period in which bleeding
lasts more than 7 days is considered to be abnormal. We call this excessive menstrual bleeding menorrhagia. There are many causes for this excessive bleeding. If there is a chance that you may have become pregnant, then this excessive bleeding could represent a miscarriage. This is one of the most common causes of menorrhagia that comes on suddenly and does not recur the next month. If your period finally stops this month, but next month the same thing happens again, then I think there are a few possibilities more likely than a miscarriage. For example, some women develop a type of benign tumor in the uterus called a fibroid. These fibroids typically do not cause a lot of pain, but they can cause excessive bleeding during your period.
Since you are already on day 16 of your period, I think it is time that you schedule an immediate appointment with your OBGYN. The reason you need to be seen sooner than later is that if your period goes on too long you can become anemic from all the blood loss. Your doctor
will likely want to do a series of tests including some routine blood work and perhaps an ultrasound
of your pelvis. Good luck.