So we can explain what the pill does with your cycle, we will briefly explain what happens before and after you ovulate. Your cycle begins on day 1 of your period, this phase is also called the follicular phase. During this time, the follicles mature and your body prepares for a possible pregnancy. The follicular phase ends with ovulation, the most important event in your cycle, after which the luteal phase begins. The best quality mature egg ruptures and travels from the ovary through the fallopian tube to the uterus, where it can be fertilized. If fertilization does not occur, the egg and the lining of the uterus that has accumulated are shed: menstruation occurs and a new cycle begins. Pretty clever circuit, right?

You can find more information about your cycle here here.

You've probably heard that the pill tricks your body into thinking you're pregnant, but that's a common misconception. The pill puts your body much more into a permanent luteal phase, that is, the phase in which ovulation is already over. 

The pill also prevents the lining of the uterus from growing properly. This means that a fertilized egg cannot implant itself. In addition, cervical mucus does not form when taking the pill, since its production depends on an unaffected hormonal balance; therefore, vaginal dryness is a common side effect of the pill. 

If you take the birth control pill and stop taking it for a week, you will have your "period" during that break. This bleeding has nothing to do with a healthy period, but is a withdrawal bleed that occurs when hormone levels, which were maintained during the pill, suddenly drop.