It's one of many possibilities - in any case, doesn't sound good!
Any low back pain, acute (started gradually or suddenly but new, discrete episode) or chronic (longstanding, as opposed to severe, which may wax and wane) should be properly assessed by your GP who will either be confident enough to diagnose on the basis of history and examination or refer you to physio for a better assessment and help with the correct course of physio.
Self diagnosis is not recommended unless you are confident about the cause and effect and happy to join the dots yourself...it sounds like you have a muscle strain/spasm more than sciatica which refers to the pinching of the nerve as it exits your backbone. This can go on to cause sciatica. But don't take my diagnosis - if it's bad and limiting you, get it looked at.
Hope you get on ok - do refer to that website I posted earlier to see what you may have...sheffieldachesandpains.com
Cheers
Rbanners
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