Spotting cd16 / implantation ??

so yesterday was only the 16th day into my cycle. I was having sex with my boyfriend and before anything happened he said "babe your bleeding". I was so shocked and surprised because I have NEVER spotted before mid cycle and I was like "wtf my period was just two weeks ago" so this whole thing was super worrisome and just odd. Then I got to thinking... could this be implantation. ? I had sex previously on CD7 and CD9. Possibility I could be pregnant from that. Anyone ever conceive early ? (Initially looked like actual blood color. But after I put a tampon in it was some light brown discharge and today there's really nothing it tapered off)