Prolonged period

For as long as I've been actively tracking my periods, about two years, I have bleed for five days consistently, starting heavy the first two days and slowing until day five. This cycle however is very different, I am currently on day 9 of bleeding, it started very light, like spotting but has been consistently normal sense, not heavy not light. I have recently started taking black cohosh for other reasons, but I can't find anything on that prolonging periods. Has anyone else had something similar or know if the cohosh could be affecting me this way? Any help is appreciated!