Please help... I really really like this guy and I knew him like five years ago. Now he doesn't even notice me?

I am 12 and in sixth grade and I just switched to middle school and left elementary school. In first grade and kindergarten I used to go to a different elementary school than what I went to in second, third, fourth, and fifth grade. And in kindergarten and first grade me and my twin sister and this guy used to be best friends and we would go to each others houses to play. Now we go to the same middle school and pretty much totally avoid eachother. We both are in band cl together on Fridays and he is also in my 6th period cl every day and I also see him staring at me occasionally. But recently he started dating like the prettiest girl in my grade... AND THEY BOTH LIKE EACH OTHER A LOT! I am so jealous of this girl too:( I walk past him in the hallway and he looks at me he whole time so I just smile at my friend that is walking with me and laugh a little. He is so sweet and sensitive and I like him so so so much. I even had my friend, which is his best friend, ask him if he likes me. And he said exactly this, " not really, no I don't" , I have gone to school with him for about four months now and the only thing I have said to him was, "hey, do you remember our black dog that we used to play with when we were little?" and " ummmm...... "Are you trying to cut in front of me in line? Cuz that is not going to happen. Sorry". And here is the worst part, during the first month that we were at school, he asked my twin sister out! Please help me I feel like I am going to cry when I look at his facebook profile:( I have never liked anyone this much ever before in my life!