Possible kidney infection?

Patient: Hi. I got a UTI last Saturday but didn’t do anything about it. Then Sunday it got really bad, burned when urinating, sharp pains, had to pee every 3 minutes and had blood in my urine. I didn’t go to the doctor but started taking antibiotics (doxycycline). 2 first the first day and then one each day. Allt he above symptoms went away in 1-2 days but 3 days ago I started having sharp pains in my back. Could I have a kidney infection even though all the other symptoms went away and I’ve been on antibiotics for a week?