My daughter is 36 wekks pregnet and having bad back pain and pressure on her vagina. Wbhat could this be.?

Labor pains? Early labor pains are called braxton-hicks contractions and are normal. You should still run your situation past your obstetrician.
Depends. Lower back pain is exceedingly common in pregnancy, especially later on, due to the extra weight being carried in the uterus. Pressure on the vagina could be due to the fetus' head pushing down on the birth canal.