Feeling so guilty to call in sick to work..

But I feel so exhausted thinking of the next day already while in bed.. I am a primary school teacher and I am dreading to go work. I feel bad for other teachers to cover my lessons and at the same time, i feel even worse thinking about my students missing out on lessons. But i just feel so exhausted and lazy thinking about having to put on a face and engage with others. I am currently 24 weeks now and FTM. Am I a bad person? What would you do if you were to be in my shoes?