Hello docs! can you tell me what could be the cause of my dull achy with sharp, painful spasms back pain?

Muscle spasm: It is difficult to tell without more history or physical exam, but if it is not radiating anywhere, just right in the same spot in your low back, then it is probably a strain or spasm of certain paraspinal muscles or occasionally hip flexors that attach to your lumbar spine. If you have any other symptoms, then it could be other things. Also, ever had kidney stones before, sometimes can feel same.