what hours should I be working while pregnant?

Shannon • Ayla Rose - 29/7/17👑🎀 Baby boy on route💙
I'm 6 weeks pregnant and I'm working 44 hours a week at the moment. I've tried to get my work to put them down but they said they've done as much as they can (used to work 50+). I'm struggling at work I'm so tired. What do I do? 
Edit: forgot to mention I work in a very busy buffet restaurant, I have to stand the whole time.