D.W.
It's OK to be freaking out.
Call your doctor today and ask what she thinks may be going on. Stay off the internet. Believe me, you don't want to start researching without proper training to assess what is in line with what you're experiencing.
Thyroid cancer is not genetic, to my knowledge. And, if you do have thyroid cancer, it is the MOST treatable cancer followed by testicular, Hodgkins, lymphoma, some skin cancers. Over 92% of patients with thyroid cancer are cured with surgical removal of the thyroid and irradiated iodine + restricted diet.
Did your doctor mention seeing an Endocrinologist?
Call today. Be firm that you are freaking out and need to know what she suspects. I went through this 2 years ago right after the birth of my daughter. Unfortunately, I have a degree in Biology, so I could read clinical papers and had already diagnosed myself before the pathology report came back. I did have cancer (Hodgkins), went through 5 months of chemo and have been fortunate to be cancer free for the past 20+ months.
Good luck! Please keep us all updated on what you learn.