i have low bleeding very low like drop.

Hi,
Welcome to ehealthforum,
If you have had unprotected intercourse and not prepared for pregnancy, you should take emergency contraception within 48-72 hours of intercourse (taking it later than this time might have same efficacy in prevention of pregnancy). The symptoms of missed periods, light periods could suggest possibility of pregnancy. Wait and watch for your 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.
Take care.