Early pregnancy symptoms?

Has anyone experienced mild pelvic cramping with implantation? My AF is due to arrive on 9/20, but I am experiencing hypersensitive nipples, tender breasts and some mild cramping since last night. I don't want to get my hopes up in case it is my AF  wanting to arrive early... Did you notice a difference in implantation v. Period cramps? Any input from those who experienced symptoms after conceiving would be appreciated!