I am 20 and have a craving to get pregnant??

So I am only 20 years old, I have a loving boyfriend and I am a student. Since I was about 17 I have wanted kids, like now. Sometimes, when I have my period I imagine it being similar to pregnant pains and I rub my tummy and feel so warm inside as I cannot wait to be pregnant!! I am so young, everyone around me couldn't think of anything worse. But I have like an insane instinct type thing going on and I really want kids bad. 
Do you guys thinks it kind of abnormal for someone of my age to have this craving for kids of my own??