What Causes A Missed Period,abdominal Cramps And Food Cravings?

Hi last year due to a eplipetic seizure i lost a pregnancyat 3 months, now my period is regularly between the 17 to the 24 due , my last period lasted two days , now i have cramps back ache n craving choclate it feels like my period is coming yet it doesn t, I ve done a urine test n it says negative , a blood test three weeks ago said the same, could it be stress or eptopic possibly im worried