Missed Period

I got an IUD late September this year, so have only had it about two months. My period is late by 13 days now and I have been testing but comes back negative. I am going to test again in the morning but wanted to get some feedback about my symptoms. Past two weeks I have been experiencing more increased back pain/migraines (already have chronic migraines and back issues), occasional lightheadedness, hot flashes, occasional severe pelvic pain, nausea, but no bleeding. Any suggestions what it might be?