Cutting corners symptoms and conditions

My daughter is 16 and was given Levaquin 500 for a sinus infection. While on the medication she was tired but not much else in the side effect category. Now here we are 4 weeks later and she has acute abdomen pain, extreme fatigue,nausea, a headache, and she has lost 21 lbs in 2 weeks. I took her to the doctor and they ran a cbc, chem 12, urinalysis, and an electrolyte panel. All came back negative. Basically my perfectly healthy little girl is suffering from this. I went back and looked at the Levaquin packet because I know it can sometimes take a few weeks AFTER medications are stopped for side effects to show themselves and of course, all her symptoms are listed.