Dental assistants/dentists help needed!

Hi! I'm 27 weeks pregnant. For the last almost two years I've had a toothache in the exact same spot (top, back left side) it almost feels more like root/gum than it does tooth. I've gone to THREE different dentists when the pain has gotten unbearable because it does slightly come and go. All three took X-rays, the last one was in May right before I became pregnant, and all three said the exact same thing. No cavity, no issue with the area im pointing out. One dentist tried mouth guard and that was a waste of money, and one drilled down the bottom tooth a little in case it was causing pressure when I bite, but still having the pain. My whole upper left jaw area hurts right now and I'm pregnant and worried! Should I tell my regular OB ? I don't want to waste going to another dentist and hearing nothing's wrong with it. It's made me feel so defeated!