Levaquin (levofloxacin) is a very good antibiotic that is commonly used to treat kidney infections and other forms of serious infections. Usually the medication is tolerated very well and doesn't cause too many side effects. Stomach upset is a definite side effect, but that can usually be eliminated or at least reduced if you make sure to take the medication on a full stomach (after a meal).
On the other hand, some of the other side effects that you are describing, such as headache
and muscle pain
, might be from the kidney infection itself and not from the medication at all.
I would recommend that you go back to see your primary care doctor
, or whichever doctor prescribed the Levaquin for you in the first place, and describe the symptoms you are experiencing. They will be able to help you determine whether these symptoms are really are a side effect of the medication or, rather, are from the kidney infection which is not fully treated yet.
I would definitely recommend that you not discontinue the antibiotic until you talk with your doctor, as doing so might allow the infection to come back. Your doctor can help determine if you should switch to a different type of antibiotic.