For Nearly A Year, I Have Had An Issue With

For nearly a year, I have had an issue with my a swollen lymph node in my neck. It's on the left side - always the same spot. It always happens within 48 hrs of my period beginning and subsides over three to four days and the pain and swelling go away. I've been to my GP three time about it (June 2014, August 2014, and December 2014) and was prescribed Augmentin (sp?). Given the side effects of such a strong antibiotic, the last time I didn't bother taking the medicine as the lymph node swelling faded away sooner than the effects of the drug. I finally got the timing right to get in to an ENT in February while the gland was swollen and the ultrasound showed an enlarged gland. The ENT offered a biopsy, but I shied away from the notion. All the doctors I have seen have been dismissive of the correlation of it being at the same time as my period. I am getting increasingly anxious about this and do not know how to proceed. Any suggestions?