What's the soonest one can have implantation bleeding?

Meg • Joyfully married since 2006. Love spending time with family & friends. Love the beach & camping.
Clear blue digital OPK said I ovulated yesterday. DH and I BD 12/27, 28, 30, and yesterday. Today there was a little pink blood when I wiped after going to the bathroom the 3rd time (nothing the 1st 2 times). Could it be? Is it too soon?