Baby Fever

I'm in college and play volleyball for the school and have about 3 years left and I am getting married in the next year. I do not know if it's natural, or because my friends are having babies, or if it is because I'm a nanny full-time and always with a baby, but I find myself crying because I want to have a baby so bad, but I can't yet. I don't know if this is normal or if I'm just a nut. I am not sure how to get over it and I need to finish school first.