4 causes 3 likely 1 unlikely.
1: If you drink to much
2: If you dont drink enough
3: if you have an infection
4: if you have kidney stones (but then the pain would be so extreme that you would need strong painkillers)
I would say probably cause 2 or 3 since you said you havent drunk too much. If 3 you need antibiotics go to a doctor and get a prescription