My boyfriend and I had unprotected sex while i was ovulating and I think I might be experiencing implantation bleeding. My "period" started a few days early and it started out light pink & sometimes dark brown. Now it is like a burnt red color. Last night it stopped completely and didnt start back for a couple of hours. it has started back and it is burnt red again but feels nothing like my regular period. I normally cramp extremely bad but now its is only a few cramps but i have lower back pain. This "period" is not like a flow and has yet to fill up a light pad. Could it be implantation bleeding?