I was prescribed 500 mg Levaquin for 10 days, after the third day...

I was prescribed 500 mg Levaquin for 10 days, after the third day I started having pain in my lower back and left shoulder. The pain got much worse and I knew there was something wrong, I googled levaquin and realized it was the drug causing my pain I discontinued the drug immediately (had 5 more pills remaining) and went to my doctor, he said he "doubts" its the levaquin...and that I should continue taking it! I insisted he gives me a different drug. He is usually very nice and always give me and my family free samples (we don't have insurance) I am really surprised that he would give me a drug like this without warning me of the side effects and even worse he refuses to acknowledge that levaquin is the cause of my pain..