Can i get medical marijuana for backpain in CA?

I strained my lowerback and its been hurting for 3yrs, somtimes my lowerback feels like it locks and it is very painfull to stand or sit, i went to the doctor 2weeks ago and got x-rays taken and he said my back was ok? he gave me painkillers but they dont work iv tryed everything, nothing works like marijuana to ease the pain,can i get medical marijuana for constent lower back pain?