Hi SarahDee,
I found the following from a PG website. Hope it helps
"When does implantation bleeding occur?
Usually 5-12 days after ovulation, so just around the time that you would be getting your period. Bleeding during ovulation is something different.
What does implantation bleeding look like?
Implantation bleeding signs are a light pink or brown colored spotting.
How long does implantation bleeding last?
The duration varies for each woman."
So basically AF is due 14 days after Ovulation. So depending on when you ovulated in theory you can bleed a day or two before AF and it could be implantation bleeding.
Cx