A girls period sees changes within her uterus. The layer of blood and the ovum (the egg that did not get impregnated) slough (fall away) off of the uterine wall and the pH (acid level) of the uterus...
Yes, see below.
Yes, you can get pregnant even if your cycle is undergoing drastic fluctuations. If your uterus has a viable lining and you have released an egg that comes into contact with a sperm,...