My Son Had A Fever For 3 Days, I Went

my son had a fever for 3 days, I went to the doctor but it looked like the fever had broken. After the doctor visit it came back and then broke again then came back again at night. Then my son's calf muscles started hurting him and though he went a day without the fever it is back again. His gums seem a bit darker than usual and the roof of his mouth is sore. Is this normal for a cold.