What Causes Stomach Cramps,nausea And Mild Fever?

My Daughter aged 13 years old, about 5' 5 and weighing approx 13.5 Stone is feeling quesy, has tummy cramps (not menstrual), generally tired. Has been off thyroxine at Consultants instruction for six months and is due to go back for a check up in June - any idea what these symptons might mean. She is slightly warm indicating a mild temperature