Sickness/work & pregnancy

I'm almost out of 12 weeks & starting to feel better, but exhausted!! I work in a special needs school so it's very go go go all the time, I leave the house at 8 & get home at 6.
I'm having 1 day off a week almost it seems. Although some days have been due to emergency doctors appointments, some just due to exhaustion. I'm feeling really really bad about it & it's stressing me out! I think people are going to think I'm using the pregnancy as an excuse, but I would love to have the energy to go in. I enjoy my job!!