The most common cause of back/neck pain is strain or injury due to bad posture during the daily routine activities like sitting, bending forwards and lifting weights etc. Lack of regular exercise to the back and abdominal muscles, age related wear and tear changes in the discs and bones in the spine, obesity are other contributory factors. Severe wear and tear changes (degenerative changes) in the spine can lead to instability and pain that is worse on certain activities. Mechanical back pain usually gets better with bed rest.
A small percentage of patients have a serious problem like a fracture, infection or tumour in the spine causing the back pain. Any pain that is not relieved by rest or is worse at rest, pain that wakes you up from sleep should be considered serious and that needs a consultation with your doctor.

If the back/neck pain is not very severe and is of a short duration, then complete bed rest for two to three days will help reduce the pain significantly. Applying ice packs and light massage with a pain balm/gel is helpful. Consult your doctor if the pain is severe, running down in to the legs/arms, not getting better with rest, night pain, if there is numbness/tingling sensation or weakness in the limbs, is associated with fever, or if the pain started after a significant injury/fall. Thorough clinical evaluation by the doctor will help identify those with possible serious causes of back pain and further investigations are advised accordingly.

Possible. But not always
Kidney problems, especially renal or ureteric stones can lead to pain in the mid and lower back, usually limited to one side, often pain radiating down to the groin or lower abdomen. There are certain indicators to differentiate pain coming from kidney or other organs in the abdomen from the pain originating in the spinal structures. In general, spine related pain is mechanical i.e., it is worse in positions where the spine is loaded like while in upright posture, walking or bending or getting up from reclined position and generally gets relieved by resting in reclined position.
Pain from the kidneys can start suddenly in any position, can be waxing and waning and may not change related to a particular posture. It may not get relieved by rest and can be severe even while reclined. These are only general indicators and it is always better to check with your doctor and get the right treatment advise.

A very common cause of back or neck pain is bad posture related stress to the spinal structures that happens during the daily routine activities. Sitting/standing posture, especially at work, has a major role in producing significant pain and disability even though the X rays/MRI of the spine may be normal.
Bad sleeping posture can lead to pain in the neck/back. Sleep is important to allow the spine to recover from the daily stresses it undergoes while we are awake. Reduced sleeping time and lack of proper sleep can lead to accumulated stress in the spine and result in pain. Lack of adequate exercises to keep the spine flexible and muscles strong is another important factor leading to pain.
So, right posture and regular exercises are the two most important treatments to prevent such pain from troubling you.
Other structures close to the spine can also lead to back pain. So if the MRI of spine is normal, further evaluation might be ordered by your doctor depending on the clinical picture.

No. It is a common perception that the spinal / epidural injection that was given in the past for anaesthesia purpose is the cause for back pain. Many patients associate their back pain to that injection as they remember it as painful event and think that the present pain is related to that procedure. Spinal anaesthesia related back pain doesn’t usually last more than 3 to 4 days and almost never beyond one week. So the back pain that continues beyond one week or that starts much later after the spinal anaesthesia is not because of that injection and it needs evaluation by your doctor to find the right cause and treat appropriately.

Not necessarily. Although disc is a predominant source of back pain, all back pains are not because of a disc prolapse. The other structures in the spine like the facet joints, ligaments, vertebrae(bones) or the muscles of the back can be the cause of pain in the back. Less commonly, pain related to abdominal organs like kidneys or pelvic organs can be perceived as back pain. Rarely, more serious conditions like infections or tumours in the spine can be the cause of pain. It is essential to see your doctor if there is significant persistent pain. There are certain red flag signs that the physicians look for to decide if further investigation is required