Believing in teenage love

I love falling in love. I love flirting and that feeling of chemistry when you meet someone new. I am actually in an exclusive relationship, and he's very important to me. I think I'm in love with him. Still, I can't help but be plagued with fears and insecurities about our relationship. The first was caused by the fact that he used to be interested in one of my friends almost right before we started dating. I quickly got over it, he never gave me any reason to think that he's still interested in her. I know he loves me, and I know he'd never be capable of hurting me on purpose, but as of a couple of days ago I can't get some thoughts out of my head. I am young, 16 years old to be precise, and I know how it is when people get in relationships at my age. They like each other, bla, bla, bla, they get together for a year or two if they're lucky, and it always ends. Then I wondered, if this relationship is doomed to fail from the start, because of our age, then what is the point? Why do I get in a relationship when I know a year with him is all I'm going to get? Why do I keep torturing myself with the idea of love, when I know in the deepest corner of my heart that as a rule this is only a fling? Why are these rules this way? This has been bothering me for a while, and I've just now managed to put it into words. I hate that things are like this, and I hate that I had to realize it, because now it seems unfair to keep on this facade that a relationship at this age will actually work out. I'm not sure if I'm being pessimistic, and I don't know what I should do. Should I try to banish these thoughts from my head or pay attention to them and give this guy the boot? The only reason I got involved with this guy was the feeling you get when you know someone is going to take care of you and do you justice as a person. I dare say I knew he loved me and genuinely felt it almost as soon as we started getting together. I knew he would be with me and that we connected in a way I don't usually do with people, and that the connection he felt was real and pure, without any side intentions like the parade of assholes I'd dated earlier that year. He was that one good, pure, warm, loving man that I'd never ever meet again. I knew when I saw him and how he was inside that I'd never meet someone like that, and I shouldn't let this pass by. He was special and I just knew it in my heart. Should I give him a chance or should I just nip it in the bud and never know what happens?