He doesn't use fb to flirt with girls. He was discrete about me. So why block me?

Honestly i've been in this position on the other side. I really liked this girl that was a little older then me and i was really happy and talktave for the first little while but i got really quite after a while cause i noticed that i really, really liked her and i got really scared i found that what happpens if she dumps me and she dosent feel the same way then im screwed so i said to myself mabye i just wont talk to her cause if i end it now at least i didnt get extreamly in to her. but i couldn't contain myself i liked her way to much. everytime she would be with another guy i would get extreamly pissed but, then i started to talk to her again and everything went back to normal but, i got a little to interested i wrote a ton of songs about her and everything and things were getting really serous. then this older guy that was like 23 tried to kick my *** and im only 17 but, i holded my own and fended him off then when i told her about it she thought i made up the whole thing and then didnt talk to me and now shes graduated and gone. In your case i think he just really liked you and didnt want to get really serious because he was afraid he was going to get hurt in the long run.