I'm sure, but too sure. Plz hlp!

So I believe I'm going through what is called implantation bleeding, but my period is due to start in 4 days. For the most part my cycle is regular so I could just be that. Howeve, if this is implantation bleeding then this would be within the time it is supposed to happen. 10 -12 days after fertilization right? . IDK how to explain rlly I can update with pictures and symptoms if that help you all help me. I just would really like to know before I take a test and it reads negative I'll be disappointed.