Anyone out there in same scenario?? I am a normal 28day men cycle and had unprotected sex on day 10, 12 and 13 of this month. On cycle day 12 I had normal more consistant discharge thinking that I ovulated.

Im not due for my period til 10/31. on cycle day 18 & 19 I woke up with heartburn and strong lower back cramps that at times would shoot down my leg. Then by morning came along and and hour or two passed I finally couldnt feel them at all. Could this be implantation cramps?? Anyone else had these?