Possible implantation cramps?

Angel
I am approximately 5 DPO. Was standing at my register at work today when I got a sharp cramping pain in my left pelvic area that was so sudden and painful I lost my breath and it almost knocked me over? Like I felt it all the way down to my knee. I have no idea where that came from and it was so random. Never felt anything like it. Any thoughts on what It might be?