Suggest Treatment For Headache Caused After Taking Eltroxin 100 Micrograms

hi my name is philomena..iv been taken eltroxin 100 micrograms for many years now....iv never had any problems with it but of late i started taken a mulitvitiam and got real bad headaches..i also get very bad cold sores on my bottom lip and when that ends it then appers inside of my nose...but i cant take anything for this as it causes the pain in my head to come back in my head again...why is there this reaction i dont take any other tablets just this eltroxin and just 1a day ....thank you.