You might not have periods if that happens. Stress can make a difference, too. Most girls and women don't feel ovulation when it happens. They don't know for sure when it actually occurs. But ovulation takes place around the middle of each menstrual cycle.
Many girls mark a calendar with an X on the days they bleed.
For most women periods will happen every 25-30 days. Keeping a calendar will help you predict when you will bleed again. It will help you know when you are going to need sanitary pads or tampons. Also, you'll be able to know if your period is late or early. And you'll have a record if you need to see a your clinician about any health problem.