Help!

My SO and I had unprotected sex while on my period and he came inside me. I was only the 3rd day of my four day period (idk if that means anything). Aunt Flo left 3 days ago and I haven't had any spotting since. My discharge has been clear and sticky like normal, but today I found some light pink discharge in my underwear. I've heard of implantation discharge, but I don't know much. Could this be implantation bleeding? Somebody help I'm so confused!!