Dog acting out possibly?

I’m almost 37 weeks pregnant, and out of no where my dog will not go to the bathroom outside in the morning before I go to work. She goes for my boyfriend every time he lets her out. She walks around the yard like she is going to go, but then she just doesn’t and goes and sits on the deck. I’ve tried leaving her outside and she just sits at the door. I’m so confused and frustrated that she’s just started doing this and choosing to go inside the house when I leave 😞