He will not leave me alone. what should i do?

i have already asked a question about this guy not leaving me alone and i had to get my boyfriend to tell him to stop talking to me because he was obsessed with me weird questions like what kind of under-where was i wearing color and everything. plus showing up at my house asking me out (he has never had a girlfriend or even kissed anybody) he is stalking me. how do i get him to stop talking me and stalking me around?