My period ended on 17 nov.had unprotected sex on 18nov.had ipill next day.today is 26 and im bleeding lightly since yesterday.can it be implanatation?

Probably not, but...: A morning-after pill can alter a cycle. Also, many women have occasional variation of their mucus discharge, some spotting between periods, a heavier period, a lighter period, or even a missed period. Having one or two of these symptoms doesn’t necessarily mean there is a medical problem, but a visit to one’s primary care or ob-gyn doctor is a good idea if symptoms are persistent or worrisome.

I pill: Bleeding doesn't usually occur with implantation - when it does the amount of blood is very small. Potential side effects w emergency contraception like i pill includes menstrual flow changes (spotting, bleeding, early or late period). This is more likely a side effect. If period is late than take a home pregnancy test.