I feel you. During three years, there was this guy who followed me in high school, he even changed his way home to bring me home after school (the fact that I never waited for him didn't stopped him). I tried to tell him that I don't even like him as a friend, I tried to be cold, to not answer him... but he kept going. After high school, he sent me mails. And when he told me he loved me and I rejected him, he told me that he was going to commit suicide if I didn't date him. I think it would have been easier if I knew I was aro at this time.
I was lucky, my friends didn't speak about love relationships a lot. But one day, I said that I would hate to marry someone who works at the same place as me, because I would be tired to see him. They looked at me as if I was an alien and says that when you love someone you want to be with him/her all the time.
Also, I'm not sure i this is an aro or an ace thing. But when I was twelve, it was the first time I saw on television girls fantasizing with the picture of a guy. I was used to see boys fantasizing on women bodys, but not the contrary. So I thought : "Men are exciting about the chest, but us women, what are we supposed to look out?" If I have been straight, I had known I suppose; but I needed to be taught what is attractive.