Brief Answer:
Can be a posture related mechanical pain.

Detailed Answer:
Hello,
Thanks for posting your query.
From description it seems to be mechanical back pain, more related to posture while working. This is less likely to be related to sciatica in which there is a nerve compression and is less related to posture change.
For pain and spasm to go you have to do back exercises to relive the spasm associated with this. Doing hot fomentation and applying muscle relaxant gel will also be helpful in relieving the spasm.
Correct your posture while sitting. Take frequent breaks during your work.
Lie on hard bed. Avoid forward bending and lifting heavy weight.
You can take anti inflammatory drug like ibuprofen to relieve pain.
In case the pain is persistent then do consult an orthopedician for an MRI scan and get oral muscle relaxants prescribed.
I hope this answers your query.
In case you have additional questions or doubts, you can forward them to me, and I shall be glad to help you out.
For future query, you can directly approach me through my profile URL http://bit.ly/Dr-Praveen-Tayal
Wishing you good health.
Regards.
Dr. Praveen Tayal.

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Brief Answer:
Needs MRI scan for proper diagnosis.

Detailed Answer:
Hello.
Thanks for writing again.
Pain only on the left side can also be related to posture. This can be a nerve related pain also. This can be diagnosed after an MRI scan.
Hope my answer is helpful.
Do accept my answer in case there are no further queries.
Regards.

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