How do I balance it all? Help!

I'm a stay at home mom of a 17 mo and I'm almost 6 weeks pregnant. I'm really struggling to deal with the exhaustion of the first trimester while also looking after my little girl. My husband works all day usually and has no set schedule so he's rarely able to offer me any assistance. I don't have any relatives to watch my daughter to give me a break and I'm beginning to get overwhelmed! Any suggestions??