Did I damage my thyroid with iodine?

I'm freaking out a little bit. Not sure what I did.

I've taken 6.25 mg of Iodine every day for about 3 years. About a month ago I reduced the dosage to 225 mcg. Now I've lost 12 pounds which is very unusual & my TSH level is less than 0.1. I'm supposed to go back for another blood test to double-check the numbers.

Can somebody tell me what the heck I've done to myself?
I felt fine all that time with 6.25 mg. Why would dropping to 225 mcg's cause problems? I've lost weight, my heart rate is up, and my head feels odd like dizzy or something.

What should I do?