First love ... why does it still hurt so much?

Let him go. He probably stopped texting because he's realized that he can't live that life that is made up in your heads. You broke up. you've moved on. Whatever the reasons for breaking up, they were there. Underneath the surface reasons ,there are hidden reasons in the back of your mind that you won't admit or face. Truths that you don't want to be real. But the truth here is that you've both moved on and its time to face the music. Don't let the past interfere with ur beautiful future. You will always love him, at least part of you will, and that is something you will have to live with. You have to accept this, and accept that what you had is gone, and can never be again. It's a loss of innocence in way. Take a deep breath, and delete his number. If he calls/texts or messages you, send him one thing saying you are moving on with you're life, and although he is a good memory, that is how you want it to remain. Tell him you have found other things in this world that make you happy and you want to embrace them, and that you'd appreciate it if he wouldn't contact you anymore. Best of luck.