Implantation

Heather • Wife 3/28/15. Mother of 4 furbabies. TTC #1
Does implantation happen 3 days before AF would show? If so, when would a test be positive? No bleeding, just had very dull cramps for about a day and then a few sharper ones. Is it possible? Estimated ovulation was on the 13th and AF due in 2 days now.