###Human: I have light bleeding about 4-5 days after the unprotected sex. What could it be? ###Assistant: Hi. This is what is typically called breakthrough bleeding (BTB). This is seen in cases of usage of birth control pills with high estrogen content of 30 micrograms of estradiol. The event is not related to unprotected sex as you had intercourse in your safe period, as you said you have two more weeks for periods. So, this bleeding started at the time of ovulation when estrogen is in excess and progesterone is limited. The thickened proliferative endometrium (uterine lining) starts breaking and causes spotting till the progesterone part of the pills become active and secretory phase ensues. My advice would be to be placed on low dose oral contraceptive pills for birth control rather than high dose pills. Then this breakthrough bleeding which is a common side effect of high dose pills can be avoided. Revert back to a gynaecologist online if there is persistent bleeding -->