why i am not getting my periods after taking unwanted72

Hi,
Welcome to ehealthforum,
If you have taken the emergency contraception (ECP) within 24-48 hours of the unprotected sexual intercourse, it should work in preventing pregnancy (provided you were not sexually active without protection after taking it). Withdrawal bleeding usually occurs within 5-7 days of taking the emergency contraceptive indicating that the pill has worked (which could be the cause for the bleeding that you experienced). Since the emergency contraceptives contain high doses of hormones, these can disrupt the normal hormonal and period pattern. Wait and watch for your next periods which can be delayed. The tests done very early in pregnancy can show you false negative results. If pregnancy is suspected, 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, further investigations would be needed to look for the underlying cause for your absent periods. Get started on treatment as indicated by your examination findings/investigation results to help you regulate your periods.
If pregnancy gets ruled out, and if you are not ready for pregnancy, but intend to remain sexually active, 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 and avoid repeat use of emergency contraception.
Take care.