Could lightening strike twice?

Patient: I have been on the depo shot for a little over four years, and I was also on it before I got pregnant the last time. I have never had a period on the shot, and now I have been for a few days now. I have been having cravings for hot fries (chips), milky ways, and big red. I am also cramping, and moody. I just started these feelings after having unprotected sex with my bf. It happened to me once before on the depo. Could it happen to me again????