lower back pain, sore nipples, pcos.... still no period!

Hi,
Welcome to ehealthforum,
Emergency contraceptive pills contain high dosages of hormones which can affect your period pattern and cause delay in your next periods. If you have taken the emergency contraceptive within 48-72 hours of the unprotected sexual intercourse, it should work in preventing pregnancy (provided you were not sexually active without protection after taking it). Wait and watch for your next periods which can be delayed. Look out for development of any other new symptoms if pregnancy is suspected. If pregnancy is suspected, or if you miss your periods, or if you have abnormal periods, 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).
If pregnancy gets ruled out, and if you are not ready for pregnancy, but intend to remain sexually active, you should consider visiting your gynecologist to get started on suitable regular birth control measures to be protected (after your periods). Be regular with birth control use as instructed. Avoid having unprotected sexual contact. 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.