Why do I keep dreaming about having a baby?

I'm 18 and ever since I was like 15 I've been having dreams about having a baby. I dreamed about having a baby bump and how sad and disappointed my dad was and (loving the satisfaction of being a rebel) and how everyone would stare at my baby bump on the bus. That was my first dream. About a month ago I had a dream about not being pregnant but actually having a baby of my own. I had a daughter and her name was Nora. Funny thing is, my mother is telling me she had a dream of me having a baby too! Now about 3 days ago, I had a dream about going to some kind of school dance and having a with a guy and then actually throwing up and finding out that I was pregnant. I was stupid, but in my dream, I was worried about being pregnant because it would throw off my exercise routine. I don't know why I'm having these dreams. I never had before or a boyfriend but these dreams are so real and so reappearing that I feel like it's trying to tell me something. What does it mean?