Anyone have af cramps at 8dpo which had been occuring since 3dpo?

i am currently 8dpo and have been having my usual af type cramps since about 4dpo. Could this be a sign that we have not been successful this cycle (again!!) and af is definitely on her way? i have read of others getting implantation cramps but not sure how many days they usually last for? I always have af cramping during the week before my af. Has anyone ever had these cramps lasting a week on and off prior to a bfp hpt?