Implantation Bleeding

When does this occur? I am not suppose to start my period until the 8th or 9th. I had a little bit of brownish discharge (very, very little). I don't think I would have even noticed had I not had just the slightest bit of cramping earlier today and was looking for an early AF when I went to the restroom. I'm worried it's too soon for implantation bleeding and I'm already out this month 🙁 This is tough, y'all.