Scared my starting dose is too high

I just got diagnosed with hypothyroidism. My lab results were - Serum TSH level 20.76 mlU/L [0.27 - 4.2] Serum free T4 level 7.2 pmol/L [12.0 - 22.01] I've been prescribed 100mcg daily of levothyroxine and I'm really anxious about starting on what feels like a really high dose. I'm only 155cm and 86lbs/39kg, so I'm short and underweight, and I'm often quite medication sensitive. Is this dose too high for me? Should I ask to be started on a lower dose or should I just try the 100mcg?