Sprintec Birth Control but no Period

It is not abnormal. Unfortunately you do not say how old you are.

As you are taking it to help with PCOS, my suggestion will be to seek a second opinion. It should not be an issue. The pill hormones should still control the androgens. And PCOS and diabetes will often go together because of the androgen levels caused by the cysts. So rather make sure it is being treated effectively. Maybe see an ObGyn if you normally see your GP. You should anyways get a gyno checkup every few years, depending on your age.

Why does this happen? The pill evens out any hormonal cycle you may have. So no hormonal ups or downs. This prevents ovulation. Not ovulating, prevents your uterus from preparing for implantation, and thus you stop menstruating.

So where does your 'period' come from when you are on the pill? When the pill hormone levels in your body drops below a certain limit, it will cause artificially caused bleeding from your uterus lining. This is called withdrawal bleeding (not menstruation which is the shedding of a prepared lining). In some women, this hormonal level may just never drop low enough to cause the bleeding. Every woman is different. Your PCOS may also contribute to this. There is no evidence that this withdrawal bleeding is medically neccisary. It does give women the comfort of a regular cycle and confirmation that they are not pregnant, so on an emotional level it may be neccisary for a lot of women.

Hope this explains a bit more than your doctor did.