my nipples darkened and i'm experiencing very minor cramping

Hi,
Welcome to ehealthforum,
If you had been sexually active without protection and if you are not on any regular birth control measures, chances of pregnancy are possible. The symptoms that you describe (delayed periods, lighter menstrual bleeding, darker areolas, mild abdominal cramps) could be few of early symptoms suggestive of pregnancy. Wait and watch for your next 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). Be in regular monitoring and follow-up with your treating doctor/gynecologist and report any new/abnormal symptoms immediately. Drink plenty of water. Take adequate rest. Maintain healthy diet and lifestyle.
Take care.