I Am Taking Thyroxine 100 I Have ETD And PET

I am taking thyroxine 100 I have ETD and PET having headachs visiting diarrhea and hearing loss with some pain and if I lower my head below my heart I lose my balance and have to crawl on floor to the bathroom last night I also had some vertigo. This is the only med I take. Hah iodine radiation to destroy thyroid 12 weeks ago. No cold or sinus problem no running nose etc this lynn am I allergic to thyroxine