sad little clingy me

Most loves that are felt from the age of thirteen to nineteen years are said to be simple crushes and short-lived. Only later does the 'real thing' come along eventually. The other loves are just so-called puppy loves.
The classic teenage love relationship looks like this:
Two teens meet, they fall madly in love. After some time their crazy lovey-doveyness dies off and the relationship is more of a routine now, based on a schedule rather than spontaneous undergoings. Finally the primary feelings and passion die down completely on one or both sides and the two teens go their separate ways.

He's the one who started it. He texted me all the time and kept talking about everything and nothing, he was the one keeping the conversation going and wanting to know what I was doing. He was the one who said 'I love you' first and asked me out. He was the one who made me want to stay with him. He did almost everything so perfectly romantically like I used to imagine it when I was a naïve thirteen-year-old that I couldn't resist.
And now I feel it dying down. There's less passion. The texts change from tons a day to just about above a dozen. Our encounters change from being lifted up and kissed to just a little peck and a 'Hi' thrown in at a whim. Conversations run dry because we've apparently talked about everything there's to talk about. 'I love you' turns into the lonely text shortcut 'ily'.
Now I'm the one trying to uphold a conversation so it doesn't become awkward, I'm the one who stays up just to get a text that he's going to sleep so he won't be texting me, I'm the one who feels the urge to tell him that I love him more than anything and that I want to spend as much time as possible with him, I'm the one who doesn't have a death wish anymore because I've found someone worth living for.

I don't want this relationship to just die down like a... like a withered pot plant or something. I don't want this to end up as a senseless thing that happened in the past and that should be forgotten as soon as possible.
I want my relationship to stay alive. To prosper. To evolve into something more.
I'm scared of failing to uphold this relationship to a person who's dearer to me than anyone. I'm scared he'll soon grow tired of me and cast me aside, with all his promises and plans left chucked into a corner. I'm scared of losing him to my own inability to be something worth loving.

/P.