@MikeMason-- I had a kidney infection last year, it causes severe lower back pain. I had never experienced something so painful before this.
Since it's an infection, it also causes fever and fatigue.
If you have these symptoms, you need to see a doctor right away, it can be very serious. If you have an infection, they will give you antibiotics. After you finish the antibiotics, you will have to get a kidney function test to make sure everything is okay.