Ttc and bleeding

My husband and I are Ttc. Took a fertility test 6 days after my af & it was positive. So we were intimate for the next 5 days! I am bleeding & my period isn't due for another 4 days and I am cramping, aching, my boobs are sensitive and I have a killer headache. Could it be implantation? Just curious it's heavy like my period. just curious!