Since how long are you having these pain ?
What dose of motrin are you taking right now ?
Any history of injury ?
Any X-Ray done ?
What is your age and sex ?
The following parts of spinal anatomy can cause pain:The large nerve roots in the low back that go to the legs and arms may be irritated The smaller nerves that innervate the spine in the low back may be irritated The large paired lower back muscles (erector spinae) may be strained The bones, ligaments or joints may be injured The intervertebral disc may be injured .
Well since it is already three days old i would recommend an X- Ray of lumasacral spine be done .
In the mean time you can take motrin 200 - 400 mg SOS . Get some Rest . Avoid weight lifting . Also Physiotherapy may be also help .Avoid stooping, bending, lifting and sitting on low chairs .
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NSAId like Ibuprofen ( motrin ) will help to decrease the pain . Soma and robaxin are muscle relaxants and can be prescribed for reducing muscle pain but i would prefer NSAID since i am not sure whether it is muscular pain or not .