Im 16 weeks and ive been having problems with sharp pain in my lower back. It radiates to my left hip, does yours radiate anywhere? What i did was go to the chiropractor and he (or she) will align your whole spine, its ah-mazing! Just make sure they know you're pregnant so they dont use objects or techniques that will harm your baby.
I have this and i am 38 weeks mine was getting so bad i told my doctor and all he did was recommend i get a pregnancy massage but i didn't have the money for it so im stuck :(