It helps if you track your cycle-like the first day of your period is day one, and then the next cycle begins again the first day of your next period. However many days there are between periods is how long your cycle is and 14 days before the first day of your period is when you ovulate-I hope that makes sense. It helps to look at a calendar, or the website I mentioned before. If you estimate that your period comes about every 4 weeks, then you could try using an ovulation predictor kit (opk) 10 days into your cycle, and take the predictor test every day until you get a positive (color match in most cases) result, then you know you're ovulating within the next day or so. An easier way is to just have sex every other day-that method works for a lot of people, and you're sure to catch one of your ovulation days, but I would suggest tracking your cycles anyway, it makes it easier to know when to expect or not expect your next period. Good luck and I hope this helped.