Don't plan on getting pregnant immediately/exactly when you want. Don't plan on getting pregnant until you are in a very stable relationship for your future child. (I don't know how long you've been with this boyfriend but that always raises a red flag in general). Don't plan on having a baby if you can't afford it on your boyfriend's income if you haven't already graduated and passed your NCLEX. Don't plan on not having a preemie and allowing your graduation to ride on having a perfectly healthy pregnancy and having no complications or special needs at the end of your last semester.
Basically, if you have been with this guy for years, you can afford a baby on his income alone, and you don't mind pregnancy complications foiling your plans of being a nurse, then you can do what you are planning to do. If those three things aren't true for you, please don't execute this plan.