Spotting after ovulation? PIC

Hi all, I am new here and I was just wondering has anyone had spotting after a confirmed opk for ovulation and knew something was wrong? It's way too early for implantation bleeding. I had it last month, 5dpo then yesterday 4dpo. Could it be that ovulation is under way again? I know some women get spotting when they are about to ovulate. But could it be something more serious, like cancer or something wrong with my insides? Any one have something similar?