Its good that you talked but think the spark was missing. There was nothing special about it. If you would ask him how big his dick is or something, that would get his atte tion. Also when you chat on FB its good to say that you just got out of shower. That makes guy think about you in a sexual way. There are even 10 text messages that makes guy think about you in sexual way by Mathew Hussey.
Not saying you have to go so low. Sure you probably have deep interesting personality and good grades in school. But it really takes a while and a lot of communication to find out how great are girl besides her looks. But guys at that age dont concentrate on single girl to find out.
I remember myself at 15 and even when beautiful girl was trowing herself at me I didnt gave a fck. Lol.
So yeah at 15 and 75 it might be hardest times with guys.But when you are 20 you should be getting most attention from guys than ever in your life. Thats the age when most girls are already given away their virginity. But many girls I chatted with said it happened to them at 17 as well as their first BF. So yeah dont worry, you have a lot of time to find a BF. At least statisticly.
This guy - your crush might not be your ultimate happuness but he might be step to your happiness. So dont be afraid to fail.
Doubt kills more dreams than failure ever will