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Variation of 5-10 days in your menstrual cycle length is considered to be normal, and can occur due to stress, hormonal imbalances, changes in diet or exercise pattern, changes in lifestyle etc. If you had been sexually active without protection during your fertile days or around your ovulation time, chances of pregnancy are possible. Wait and watch for your next expected periods. Look out for development of any other new symptoms if pregnancy is suspected. If periods do not start within 10 days of expected period dates, or if you get abnormal periods, or if you suspect chances of pregnancy, consider visiting your doctor/gynecologist at the earliest for thorough examination (to confirm pregnancy related changes/signs in body) and blood/serum HCG level test (to confirm/rule out pregnancy accurately).
Take care.