Just need some advice.

AF was due Tuesday and I'm always on time, however I've still not come on but have been having very mild on and off cramping since Sunday :/  but no sign of any bleeding and discharge is still normal.  Is it possible to still be implanting at this time or is it something else to do with anything happening inside? Has anyone else experienced this? Don't want to be taking a test and then feeling disappointed when it's BFN