Lara,
Just a comment--have you researched Armour thyroid? It's a natural thyroid replacement from pigs, and contains T4 as well as T3, unlike Synthroid which only has T4. I tried Synthroid at first, but didn't get any good results. The Armour took away my achiness, tiredness, and has helped with weight loss. Worked for me.
Armour Thyroid and Thyrolar: Alternatives to Synthroid and the Other T4-Only Drugs
Elisabeth