breast tenderness and some weird feelings in my stomach?

Hi,
Welcome to ehealthforum,
There can be alterations in period pattern due to stress, change of lifestyle, change of place/time zone, change in diet and exercise levels etc. If you had taken the emergency contraceptive within 24 hours of unprotected sexual contact, then it should help in preventing pregnancy (provided you were not sexually active after taking it). Withdrawal bleeding occurs within 5-7 days of taking the pill indicating that it has worked (which might not occur if it is taken closer to periods). Since these pills contain high dosages of hormones, these affect the hormonal and period pattern causing changes in your periods. Wait and watch for your periods and observe them for next 2-3 cycles. The symptoms that you describe could be associated with hormonal changes and ovulation. Visit your doctor/gynecologist for further evaluation if next periods do not start within 10 days or if you suspect chances of pregnancy, or if you develop any other new symptoms. 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 if you are not ready for pregnancy.
Take care.