Back pain 35 weeks

Lauren • Loving this blessed life with my husband and baby girl! Can't wait to see what more God will do with our lives!
I haven't had any back pain my entire pregnancy and I'm now 35 weeks. I woke up Monday in excruciating random pain in my back. My doctor said I had a UTI (completely asymptomatic seriously no regular signs of a UTI) on Monday, gave me an antibiotic and sent me on my way (I did realize some discomfort I was having in my stomach must have been the UTI because my stomach has felt a lot better LOL). Wednesday, the pain in my back was worse so I returned to the doctor. She said I didn't show any symptoms of a kidney infection, but my muscles were tight. She prescribed me a muscle relaxer and sent me home (of course even though it's a cat. B I'm not taking if). Thursday and Friday pain was the same. Today the pain is horrible just absolutely horrible. 
My question: did anyone else have a kidney stones or a kidney infection without any regular symptoms during their pregnancy? She wants me to come back tomorrow for a checkup and I'm wondering if I should push a little bit harder for like an extra test or further examination? OR is this just normal pregnancy pain and I've just been blessed not having the normal pains until now?