Period came 10 days early?

Hi everyone, yesterday i had brown spotting but today I seem to be bleeding fresh blood. It’s a light bleed, maybe because it’s just the first day. My period is not due for another 10-12 days. It’s not implantation bleeding as the blood did show up in my urine and I haven’t had sex since February. I should mention that two months ago, on February 10th, I was sexually assaulted and took Plan B. However, my next period in March came on time so I thought my cycle had gone back to normal after the Plan B. Does anyone know what the cause of this bleeding could be?