I have lower back pain especially on the left side. I thought it was related to physical effort but it has increased every day. I got some labs for a UTI but they came back negative, the doctor said it could be because I am taking cranberry pills. Could this be the symptom for something serious?
Dear patient cranberry pills has no relation to back pain. If UTI is ruled out possible cause will be back pain of muscular origin or instability.  I would like to advise X-ray of lumbosacral spine anteroposterior and lateral views. Please get it done from the radiology center nearby you. Meanwhile, start tab ibuprofen 400 mg twice a day for pain relief. Local application of hot water bag will help in pain relief. If X-ray is abnormal you need to consult orthopedic surgeon nearby your area.