Did I experience implant bleeding

So my Calendar is accurate on my period so here's my Qs, my husband and i had sex June 10th 11th 12th and 13th we had sex, no condoms. Had sex again on the 15th and 16th. On the 18th and 19th I had light spotting, pink-ish brown color. I know it wasn't from rough sex. Is that implantation? Or just random bleeding? I'm 3 days away from my period. Boobs hurt, lower back hurts.