How do u 2 get this guy to stop??????

ok well i was at my freinds house and she lives by a gas staion so we whent there and got stuff and well we walk by her naber and well he is 17 and he walked out and followed us. well after i left her house and walked home he fallowed me. he came up to me and said thaqt he has liked me for awile and he cant stop thinking about me. and well asked me out i told him i had a bf who i really love and just wanted to be freinds and plus your to oild for me. he told me that he not gonna stop thinking about. cause im only girl for him. now its been a week and he is at my house like every day how do i get him to stop.