Implantation 5dp or is my opk not reliable!

I used my regular OPK this cycle - it indicated that I ovulated on Day 9 of a 28 day cycle. I seem to ovulate earlier - this test has shown the same other months. My husband and I are trying our best to conceive. On day 14, after a gym work out, I began mild cramping and lite bleeding. This is something that I would have attributed to ovulating before using OPKs, however, this time I am not sure. Would this be a simple case of the OPK being incorrect or did I experience implantation bleeding?

To tell you the truth, I have noticed a lot of women reading OPK'S incorrectly :/

Have you considered an electronic fertility monitor?

On a 28 day cycle, it would be highly unlikely to ovulate on day 9.

It would also take longer than 5 days for implantation to occur. We tell women that implantation takes at least 6-7 days usually.