26 weeks... exhausted and anxious

I'm 26 weeks pregnant with hypothyroidism. They just upped my dosage again about 3 weeks ago and I am SO tired. I could sleep all day! No matter how much I sleep, it doesn't seem like enough. I've been staying home from working (I'm a sub teacher) and this is making me anxious because I want to help support my family but I'm also so tired that I feel like I can't function. Anyone have this happen?