Sure. Lots of things can cause you to skip a period including exercising a lot (like in the middle of your cross country season), stress (like final exams), and just a fluke. Of course pregnancy can cause you to miss your period too. So if you've even come close to having sex, even if the guy didn't come inside you, you should do a pregnancy test to be sure. If you go for more than three cycles without getting a period, even if there's no chance you are pregnant, you should see a healthcare professional. Even though skipping your period for longish chunks of time can seem like an easy way to live, it isn't so great for your body overall. The hormones that cause your period and the cycle that leads up to it are also really important to strengthen your bones. So be sure to talk to your healthcare professional if you are going more than three cycles without your period, or your bones might regret it later!
Just so you know, when it comes to periods, there's really no such thing as normal. My roommate in college kept missing her period, and her doctor told her it was excessive stress. If you're sexually active, you should take a pregnancy test to be sure. But, either way, if it's in some way out of the ordinary for you, or you're missing three or more periods in a row, you should talk to your healthcare professional.
There are lots of reasons you can miss your period. Don't freak out, there are more reasons than just being pregnant for a missed period. Have you been going through a lot of stress lately? That can cause a late or missed period. As well as extreme exercise, weight loss or weight gain, eating disorders, or it could be your body still working out your cycle. However, if it is happening often - where you only have a period every few months or so, you should certainly talk to a healthcare professional.
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