I take Eltroxin for thyroid - what medication can I take for migraines?

I have an under active thyroid and take 'Eltroxin'. I get occasional migraines with vision problems. What can I get 'over the counter' for migraines that won't adversely affect the thyroid medication? I am a 66 year old female. I also take 'Simvastatin' for high cholesterol