Horrible Back Pain @ 30 Weeks

For the last few weeks I've been having constant (never going away) lower back pain, it's so low that it's almost practically in my butt and when I lay down at night and wake up to go to the bathroom (which happens multiple times😂) the pain is like in my butt/leg joint area (don't know exactly what to call it) but it hurts so much I practically limp to the toilet and back to bed. I went to the doctor for it and they tested me for all kinds of things and diagnosed me with a yeast infection. Which I'm not saying they're wrong but I have none of the symptoms of one and I never heard of a yeast infection that causes lower back pain. Could the back pain be something else or is it just the joys of being pregnant?