As long as you don't have a fever and are not in too much pain, then you do not need to go to a doctor. Beware, lower back pain can be a sign of an infection in your kidneys and should not be ignored. Get cranberry capsules, take the maximum dosage for at least two week. Drink lots of water, more than the normal 8 8ox glasses. No caffeine, no sugar, no spicy food, minimal or no salt.
If you're into natural remedies then take cranberry supplements. You can also just drink the juice, but make sure it says it's really cranberry juice on the label. Also, you can get an over the counter called CYSTEX. It relieves symptoms and also fights the infection. It's the only thing that works for me! Good luck!
P.S. If it gets too bad or too uncomfortable like you feel you can't leave the toilet, just go to the Dr. It's not worth risking kidney problems.