abnormally light flow. Could I be pregnant?

Hi,
Welcome to ehealthforum,
Having intercourse during or close to your period time can cause period pattern abnormalities due to hormonal changes. If you had unprotected intercourse close to the end of your periods, then you could be at risk for pregnancy (for a regular menstrual cycle of 28-30 days, the usual fertile days would lie between day 8-18 taking day 1 as first day of bleeding). If you were not ready for pregnancy, you should have considered using emergency contraception within 24-48 hours of unprotected intercourse to prevent pregnancy. Wait and watch for your next periods. If you suspect chances of pregnancy, look out for development of any new symptoms suggestive of pregnancy. If you suspect chances of pregnancy, or if periods do not start within 10 days of expected period dates (sometimes they can be delayed by 5-10 days due to stress), or if you develop any new symptoms suggestive of pregnancy, or if you get abnormal periods, you should consider visiting your doctor/gynecologist for further 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 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.
Take care.