no

The endometrial lining.

The typical menstrual cycle is 28 days, but it is considered to be normal as long as it is +/- 7 days of this, as long as the spacing remains constant. Though it should be noted that women may have irregular periods for the first few years, and the last few years of their reproductive life.

Your menstrual cycle could have been mistaken for implantation bleeding. I recommend that you take a pregnancy tests to confirm.

If that happens often you should go to a doctor for a checkup.