Is this to early? normal? 20 year old needs help?

I have been dating this guy for two months now, and i dont know from the moment i met him i had erflies in my tummy. But now hes brining up the topic of one day we will be married and have kids and everything like that. How can he even know he wants that after two months (we are both 20). I can see us spending along time, but even the thought of him thinking about marrying me so early is strange. help.