pain in right side of abdomen

My husband has had pain on the right hand side of abdomen (at the waist level) for 3 weeks.  He wen to the doctor and they treated him for divirticulaties and  gave him penicillin for 10 days although the blood tests showed now infection.  After 10 days the pain is still there, although much less and his bowel movement is back to normal.  Now he is being sent for further analysis.  What do you think it could be.  The pain is less after he did the penicillin treatment is it has not gone away completely.  He still has to take a pain killer once in a while.  Please help me.