IMPLANTATION BLEEDING TMI

Help, so eve has my af scheduled to arrive in 2 days time. I don’t know when I ovulate whatsoever but according to eve it was the 21st August. Could this be implantation bleeding and maybe I have ovulated later? I’m having dull backache that I’ve had for a couple days but no cramps like I usually do! And when I went to wipe 20 mins later there was nothing.