Lower back pain

I'm 9 weeks pregnant and have been having AWFUL back pain since week 6 it's gotten worse it's a really sharp pain in my tail bone sometimes even effecting my left leg. I cried walking from my bed to my living room (Literally not even 10 steps) what could be the issue.. It's not miscarriage I had an ultrasound a few days ago and my baby is perfect. Just super miserable