I agree to you that a MRI would be helpful. The pain you have will be treated on the lines of low backache. Your increased frequency of urination can be because of pelvic floor weakness and will require what we call as Kegal exercise.
Click here to read about these exercises.
This low backache and hip radiation (radiculopathy) can be related to your increased exertion or prolonges sitting, as you mentioned. This is extremely common affecting 80%-90% of adult men and women between the ages of 30 and 50 years of age.
Most backache will be so called simple low back pain in which the symptoms by definition cannot be ascribed to a particular pathology. Simple low back ache is also called uncomplicated or non-specific low back pain and will vary with posture, activity, time and treatment. Radicular (or nerve root pain) will occur with low back pain. Sciatica is a lay term for pain extending into the leg (buttock, thigh, calf or heel).
This has the following management principles:
1) Back care in the activities of daily living.
Back education and back school: It teaches the patient basic body mechanics, such as the correct posture for standing, standing at a desk or drawing board, sitting, brushing teeth, washing the face, pushing and pulling a weight, lifting a weight, getting in and out of bed, sleeping, getting into a car, and sitting in a car. Back school also teaches patients the proper and improper behaviors when their back is painful in case they have to sit, bend forward, lie down, cough, or sneeze.
a) Avoid activities which increases the pain.
c) Avoid bending at 90 degrees
d) Pushing and pulling should be avoided till pain subsides
f) Avoid prolonged sitting and standing
g) Avoid sitting or sleeping on floor
2) Anti-inflammatory analgesics like ibuprofen, analgesics and muscle relaxants
3) Local analgesic gels or sprays
4) Hot fomentation
5) Electrotherapy like trans cutaneous electrical nerve stimulation: done by Physical therapist. Other thing are ice packs, heating pads, electrical stimulation, phonophoresis, iontophoresis, relaxation, and biofeedback.
6) Good supervised physiotherapy: Floor exercises consist of abdominal bracing, modified sit-ups, double-knee-to-chest or low back stretches, seat lifts, mountain and sag exercises, knee-to-elbow exercises, hamstring stretches, extension exercises, and extension flexibility exercises. Swimming exercises are some of the best activities for back pain.
7) Lumbosacral corset or support
8) Epidural steroid shots, if nor response by physical therapy.
9) Surgery is last resort, if all conservative therpy faill
10) If obese reduce weight (for long term management).
Please feel free, if you have further questions.