Talk to Gynecologist on Dull Pain (Pregnant Woman)

Experiencing dull pain since 3 days usually rises during afternoon, non radiating pain, lower left side of the back, cause: idiopathic, pregnant since 7 days, first pregnancy, weight 47, female, age 27, no past medical history of any type of illness, no use of medication, not even pain killer, mild signs and symptoms of UTI and for that she's taking cranberry juice.

Please suggest a suitable remedy or solution and what is the actual cause of the pain.