The best thing you can do for a kidney infection, or in your case, since you are not sure if it is or not, is to push fluids. You need to drink plenty of water and things like cranberry juice to help flush out your system. You can also take something like Tylenol or Advil for the back and flank pain (as long as you are not allergic to either one) and get plenty of rest.
I would suggest that if you begin to run a fever, or have blood in your urine, that you let the Dr know that you will be seeing on Thursday in case he/she wants to see you before then. Also, if you begin to have pain while urinating, you can take some over the counter AZO Standard tablets sold at your local big chain store. It is basically a urinary numbing type agent but you should only take these on a temporary basis (for only a couple of days) and be aware it can make your urine a bright orange color and can sometimes stain contact lenses.
Hope this helps!
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