If you've had this for several days and it's either getting worse or not getting better, it's best to see your doc.

If you're not having any trouble urinating....no pain, burning, etc....it's not likely that it's an infection....BUT, if it is an infection it MUST be treated properly or you risk damaging your kidney.

If it's in the kidney area and you're also having weakness in your leg it sounds to me like it's more likely that it's your back causing problems. If it's a simple muscle pull it should be gone, or at least deminished, in 4-5 days. BUT, if you're having weakness, tingling, other symptoms it could be caused by nerve compression due to a disc problem.

In any case, I'd recomend seeing your doc. I'd ratehr see you go and find out it's something minor than not go and find out it's serious.

Edited to add that pain is never normal. Pain is your body's way of telling you something is wrong.