Is there a time limit at how long you should wait to get a biopsy of thyroid gland. pet scan showed very high positive but biopsy is needed to confirm. been on going for 3 yrs now. been growing rapidly over 6 months. how do i get my dr to help me?

You probably mean biopsy of a thyroid NODULE which has gotten bigger in the last 6 months with suspicious PET scan result, I assume. I am surprised that you have not been referred for the biopsy. In general, if malignant disease is suspected, biopsy should be done as soon as possible. You can request a second opinion or a referral to an ENT doctor.