I just wanted to chime in with my experience -
I had what I believed to be implantation bleeding and cramping, as well as a dip in my temperature at 4DPO (I know, early, but I really think that was it for me). I then began testing at 6DPO but didn't get a positive result until 10DPO (well actually a very light

on 9DPO).
I would wait if you can, but it never hurts to POAS as long as it's not a digi (too expensive!!) -- Can ya tell I'm a POAS pusher???