Hello. My daughter is 9, yr old , 60 lbs. Finished amoxcillin yesterday for sinus infection. Had stomach pain with that drug. (assuming it was from that) Saw doc again today because she was feeling worse, (low grade fever for days on and off, weak, sore throat, cough, achy) tested for mono : negative. He prescribed azithromycin for the sinus infection that wasn t taken away with amoxicilin. My daughter took it at 4 pm. It s 9 pm and she s almost crying in bed saying how badly her stomach is hurting. Is this a normal side effect?? Thank you.