It's not at all uncommon for women to suffer from thyroid deficiency. I asked my dermatoligist why my hair kept breaking off and he ordered a TSH (thyroid stimulating hormone) test. Just a blood draw. The mechanism is this: TSH will be elevated if the thyroid gland function is weak. When your T-3, T-4 (Those are the potential and active forms of the thyroid hormone.) are low, the pituitary gland releases TSH to turn thyroid production "on." If TSH is elevated, that means the thyroid is not responding adequately. The treatment is just an inexpensive tablet of T-4 was once a day, calibrated to your blood test and (ideally but not usually) to your symptoms. It's much easier to treat a test result than a person.

That's adequate more often than not though, so...
You can have effects beyond sluggishness & weight gain... cardiac & other systemic stuff but I don't remember the details. You should just ask your doctor; she prolly won't need to see you. Just do the telehealth thing. You can take your own BP/heart rate & temp. I'm sure your parents will have those instruments on hand and the Fitbit will also tell you your heart rate. I felt a lot more energetic after I started taking Synthroid. It's not a panacea, but at least you're starting from a foundation of a reasonably level endocrine playing field.