It would be helpful for you to get some blood work done. At the very least, you need TSH, Free T3 and Free T4; depending on those results, you will want to get tested for antibodies.
You also need to have an ultra sound to check for nodules on your thyroid.
Do you have any symptoms of hypothyroidism? If so, which?
You might have a thyroid goitre. You would need to go to a doctor and ask them to do a neck check. You can do one yourself. It involves standing in front of a mirror in good light. Take a sip of water, hold it in your mouth, then hold your head up slightly and then swallow. If you see something obviously 'pushing' out of your neck on the side of your voicebox area, you will know you have a goitre. A doctor will feel for one when you swallow.
Get the doctor to have a look.