Okay mommies...

So we have three dogs; the youngest is 5 months old and we have a baby boy due in February. The puppy is doing better with potty training but he still wakes up around 4 a.m. to go to the bathroom. And every time this happens I am the one who takes the puppy outside while my fiancé is dead asleep. I am getting extremely frustrated, almost angry that he is not sharing this responsibility and it concerns me because it makes me wonder if this is a peak into what is to come once our son is born. Have any of you experienced a a similar situation? If so, how did you handle/fix it?