First, don't stress too much. And I know that's easier said than done when you're not quite sure what's going on with your body. "There are a number of reasons why you can miss your period, aside from pregnancy," Mysore says. "Some of these reasons can be normal changes that happen in life, and others can be the body's reaction to external triggers."
If you're sexually active and miss your period, Mysore says you should take a pregnancy test to ensure you're not pregnant. The Cleveland Clinic says you should wait five to 10 days after your period is late to take a test.
"If your pregnancy test is negative, I always suggest reviewing your symptoms and missed period with your primary care provider or gynecologist," Mysore explains. "It's important to figure out the reason why it's late or skipped one month. It might be totally fine to wait and see what happens with time, but it's always a good idea to review that decision with your doctor first." This idea is the same even if you aren't sexually active but missed your period.