Kidneys or severe indigestion?

sharp knife pains in/around belly button with pain in back and burning when pee?????

[OliveLilly]

This sounds like a Urinary tract infection. Do you have fever? If it hurts when you urinate, is there blood in the urine, or is it cloudy?
Do you drink alot of carbonated beverages, or coffee? Yes to any of these questions would strongly indicate a urinary tract infection which could turn serious very quickly if left untreated.

Cut out softdrinks, coffee, and anything with caffeine for a few days. Drink only water and cranberry juice (try to get the "no sugar added" kind to minimize calories) and see if that helps.

If you get a fever, or the pain persists, see a doctor and let them take a urine sample, this will tell you if you have a UTI.

[sanatogen]

Low back pain and pain/burning  during passing water, are most of the time due to urinary tract infection.    This needs investigation and doctor can treat it
with antibiotics but your doctor know the best.   Recurrent urine infection
needs investigations.