I too felt worse on my first 6 days of synthroid then I felt better. I just had a TT and was put back on the same dose and am still feeling ok so give it some time for your body to adjust. I know that 3 weeks seems a big long and too me I would be insisting on something after 2 weeks, heck, after one week I was insane, you want to feel better.
I agree with lady, why the caffiene? That is my one indulgence in life. That is the first thing I wanted after my surgery after the ice chips, a cafe mocha from startbuck's

mmmmmmmmm have had about 10 of them since last Tuesday!
Maybe the caffiene withdrawl is too hard on you?? That is what I am thinking it could be too.
Best of luck,
Karen