Over the last 3 mths i hurt my back now in the last 3 days i hurt my back again it is the lower part of my back.. what is the cause?

Lumbar Strain: Low back strain is common. Back pain often is the result de-conditioned muscles in the low back. The cause of low back spasm can be nerve irritation, muscle spasm or both. And either one can cause the other. A routine of low back strengthening can help prevent such injuries. Tai Chi and postural Yoga are good options to investigate. NSAIDs, hydration and heat can help reduce pain following injury.

Please clarify: If you have injured your back and it hasn't fully healed, it is easy to re-injure it more easily. Try using some ice on your back and take some anti-inflammatories for a week. If it is still hurting, see a local doctor.

Lumbar Strain: The most likely cause is a lumbar strain -muscles spasms (myofascial pain) that and can also cause your vertebra to be pulled out of alignment. Common home treatments include Ibuprofen or Naproxen combined with Tylenol (acetaminophen) as directed on the boxes. Many times it resolves on its own. If not, a doctor visit can give a more definitive diagnosis after an exam. Trigger Point Injections might cure.