Pinched nerves in the spine can cause serious back pain. Any pressure applied to a nerve by surrounding muscles, bones or tissue will produce irritation and will disrupt the nerve's functioning.  Symptoms of a pinched nerve range from aches and pains to numbness to a weakening of muscles.
Fibrous pads or disks separate spinal vertebrae from one another. The outer layer of the disc is strong and flexible, encasing a soft, jellylike core. When strain or injury weakens the outer layer, the condition known as a herniated disc can occur. This causes the disk to bulge and press against, one of the spinal nerves. This results in severe pain.

This condition popularly known as a slipped disc tends to occur in the parts of the spine that are the most mobile: the lower back (lumbar spine) and neck (cervical spine). Heavy lifting, obesity and contact sports can contribute to the problem.

A pinched nerve can occur as the result of pregnancy, repetitive motions or a joint disease. Thankfully, a pinched nerve generally heals in a few days to a few weeks. Chronic cases can result from persistent irritation of the affected nerve. In some cases, damage to the nerve can become permanent.
 

Back pain during pregnancy is fairly common however low back pain of long duration (several weeks or months) during pregnancy is a predictor for post partum back pain (pain after birth). For this reason, pregnant women are encouraged to seek appropriate treatment for back pain during pregnancy.

Likewise, any post partum pain that lasts longer than six to eight weeks should be treated in order to avoid chronic or recurring back problems
To help make your pregnancy as pleasant as possible and facilitate an easier delivery, back pain should be always be addressed as quickly as possible and managed throughout the pregnancy.
 

A pulled muscle (also referred to as a muscle strain) causes most episodes of back pain.  When injured the muscles can become inflamed and spasm, causing low back pain and significant stiffness

A pulled back muscle can create a surprising amount of pain. However, not much can be done for a strained back muscle except for rest, applying hot and cold therapy and taking pain relievers.

Ice massage and ice application is generally most helpful during the first 48 hours following an injury that strains the back muscles. After this initial period, heat therapy is probably more beneficial to the healing process. For some people, alternating heat therapy with cold application such as ice massage therapy provides the most pain relief.

Moist heat, such as a warm bath or whirlpool, is thought to aid the healing process by increasing circulation and relaxing muscle spasms.