Pain Relief From Dysmenorrhea Employing taVNS

The goal of this clinical trial is to determine if transauricular vagal nerve stimulation (taVNS) is effective in treating moderate dysmenorrhea. The main question it aims to answer is: • Does taVNS reduce the number of times participants suffering from dysmenorrhea need to use rescue medication during menstruation? Researchers will compare taVNS stimulation with a sham stimulation (a look-alike procedure that does not stimulate the vagus nerve) to assess whether taVNS is effective in treating moderate dysmenorrhea. Participants will: * Undergo taVNS for 2 months and sham stimulation for another 2 months, each for 5 days per month, starting 2 days before the expected beginning of their menstrual cycle. * Visit the clinic twice a month for checkups and tests. * Keep a diary to record their pain levels and the number of times they use rescue medication. * Undergo functional magnetic resonance imagine two times (one after the end of the first use of taVNS and another after the end of the first use of SHAM stimulation).