Help !

I took a plan the day I ended my period or the day after due to inter course leading to having to take it and seem to get another period a week later and after that again intercourse twice which also lead to more tmi being cummed it which no protection was used due to how plan b made me feel it’s been a couple days to 3 weeks since then and I’m lightly bleeding again as of last night with just that time using bathroom now it’s brown just finished a 3 day weekend with intercouse again no protection , why ? I only read people bleed once from it and wouldn’t my period come later since I already had my period and then bleed again a walk later ?