It sounds like you have frightened yourself with thoughts about the possibility of being hypothyroid after learning that your cousin has been diagnosed and it runs in the family. Please see your doctor for a simple blood test to ease your fears of wondering and what-if thinking.

I have Hashimotot's hypothyroidism. I take a thyroid repleacement medication and my thyroid is checked with the simple blood test periodically. When my thyroid is not working as it should, I feel an extreme fatigue that no amount of rest or caffeine or anything can affect, my skin gets very dry--especially my hands which get dry and rough, digestion slows so constipation can occur, my thinking slows like thinking does when a person is fatigued or doesn't feel well. When the medication dosage is where it should be, I feel great with no symptoms.

I hope you will relieve your worries with a visit to your doctor.