the morning after pill. 2 days later I started antibiotics?

Hi,
Welcome to ehealthforum,
If you have taken the emergency contraceptive pills (ECP) within 48 hours of the unprotected sexual contact, it should work in preventing pregnancy. Since it contains high doses of hormones, it can disrupt your normal hormonal pattern, and cause bleeding and period abnormalities. Antibiotics are known to affect the efficacy of hormonal birth control pills. If you had been sexually active (without additional protection) while being on the antibiotics, then chances of pregnancy cannot be ruled out completely. The lighter bleeding could be due to hormonal upset or even pregnancy. If you suspect to be pregnant (or if you are having any new symptoms suggestive of pregnancy), you should consider visiting your gynecologist/obstetrician for examination (to confirm pregnancy related changes/signs in body) and blood/serum HCG level test (to confirm/rule out pregnancy accurately). Take adequate rest. Drink plenty of water. Maintain healthy diet. Do not start with the next pack of birth control pills if pregnancy is suspected (or unless pregnancy gets ruled out).
Take care.