It may be caused by a urinary tract infection because the female urethra is shorter, only about 4 cm, and the opening of the urethra is located above the vaginal opening. During sex, bacteria around the urethral opening can be squeezed into the bladder and cause a urinary tract infection, resulting in frequent, urgent and painful urination. In addition, the pill’s main ingredient, nonipramine, can disrupt the normal vaginal flora and increase the risk of urinary tract infections.