ano ba ang implantayion bleeding

last n ngka period aq is march 23, so inaasahan q mgkkroon aq ng april 23, pero ndi aq ngkaroon tpos this april 27 ngkaroon aq pero mhina lng n dark brown n discharge tpos ngcacrumps ung puson q at sobrang sakit ng ktawan q,ano po b ibig sbhin nun??