Implantation cramping

Desiree • Ttc baby #1 after a miscarriage back in October 2013.
Has anybody experienced cramping during implantation? If so, what did it feel like and how long did it last? I'm 7dpo and had a few twinges yesterday and today just a little crampy (doesn't feel the same as af cramps though).  I normally don't get cramps leading up to my af but I'm kind of feeling discouraged thinking it's just a sign of my af.