Toddlers and pregnancy

Ok so,, Im 18 And I took on my 2 sisters. (2&3 years old). Our mum left and they had to go to a home but as soon as I was legal age I got them the hell outta there. 
They are my whole world and they drive me completely up the wall! But I'm 10 weeks pregnant with my first babies🍼🍼  and I'm Sooo tired!😫
My fiancée works 10-6 mon-fri and as soon as he gets in he takes them off my hands 
But I'm so friggin tired. I literally pass out while they're playing and I've had so much morning sickness! 
How do you women do it? What keeps you going?😭😫