DAMN! Your drawins are great! I can draw fairly well but I have sketch lines and erase marks all over mine though, you do it so cleanly, course I believe that scanners actually makes mistakes less noticable, mine look better on the pc.
hope you like it
as for the cleanness ice, you should try sketching with a lighter pencil (maybe a 3h) and then use your regular pencil (hb) so it doesn't look messy if you have to erase anything