I am 16 and want a baby, why cant I stop thinking about it!?

I know its not "acceptable" to have a baby at 16 and its not that I want to mess up my schooling and future plans. It just drives me crazy sometimes.. Me and my boyfriend have been together for about a year and two months and he wants kids when we finish college which is the best idea but I cant stop thinking about wanting a baby and being a mama. I know they aren't a bundle of joy and its HARD work being a parent but something in me just breaks every time I see a little baby. when i took child physiology 2 years ago I loved it and I loved taking the fake baby home and waking up in the middle of the night to feed him and change his diaper. I want to become a neonatal nurse I love working with them so much and caring for them. I need this want to stop until me and my boy friend are ready I just don't know how.. any advice or tips that could help? and please no negative or rude comments I know I am too young.