anxiety & thyroid problems

I have had gad for about ten years as well as hypothyroidism for 17 years. I have been taking synthroid and amitriptyline for these conditions. Quit taking amitriptyline in 2008 on my own. In june of 2009 had blood work done as I was having a lot of anxiety symptoms(nervousness,burping constantly,disturbed sleep,aching legsbelow knees, aching shoulders and arms,headaches,edgey jittery feeling, can't sit still etc.etc.)doctor checked thyroid. My results showed low TSH and high FT4. Decreades my synthroid to 112mg.  In August 2009 my bloodwork showed TSH coming up slowly and FT4 coming down. My thyroid is being over stimulated. Again meds decreased to 100mg.
My problem is that I don't know if my persistnet anxiety is being caused just by the thyroid or if it's a combination of both making the symptoms seem so very severe.
If anyone has any input or similar experience I'd sure appreciate hearing from you. My next visit to doctor is Sept. 11 and I'm not sure I can take this much longer. Doctor also gave me script for amitriptyline again but I'm scared to take the two together now that the thyroid is over stimulated.
Thanks
Mama D