Hi, My Husband Has Been Sick For The Past 2

Hi, my husband has been sick for the past 2 weeks. It started with a week of diaherrea and then last week he had really bad tonsils and fever for about 4 days. Took him to the doctor and they gave him antibiotics for tonsil infection. Now this week he has complained about back pain, however, the back pain has now left him and moved to 3 inches bellow his belly button. It does no hurt him when he puts pressure in the area, in fact, he says it makes it feel slightly better. What could it be?