Ooooh I love a guilty Dustin that is irrevocably in love with El but also does not want to be. It goes against everything he thinks of himself. He's loyal to his friends first and foremost and him being capable of such a breakage of "guy code" as to fall in love, actual love, for his best friend's ex-girlfriend eats him alive.
And it's also breaking El's trust, too! She seeks him out as a friend, it feels so wrong to feel the things he feels when El is around him. He wants to be the one there for her, he wants to be the one to make her smile and laugh, he wants to be someone she trusts, and most of all he wants to be honest with her, because it's what she deserves—but he can't. Not with this.
And, to add insult to injury, El is a very physically affectionate person; the closer your relationship to her becomes, the more she feels like touching you. Holding hands, leaning on you, hugging you, and the forehead touches—the goddamn forehead touches. Those are a special kind of torture. The way she hugs Dustin and holds his face between her hands, and stays there, with her forehead pressed against his, at the same time incredibly close but miles apart from what Dustin can't help but want. In those moments, he feels her breath against his skin, and has to close his eyes to not do something incredibly stupid that will ruin everything.
With Max, it was different. He wasn't in love with her, for one, and he went to camp shortly after and met Suzie anyways. He had someone to whom he could direct all that romantic desire, and after he came back home, he was fine. He could be around Max and feel none of what he was feeling before. But with El? Nothing helps. Distance doesn't help, exposure doesn't help—all it takes is one honest smile towards him and he feels his heart aching in his chest.
When Dustin lets his mind wander, he thinks about how they would be as a couple. And it doesn't look that different from the way they are as friends. In fact, it looks nice. It seems like something El might want, as well, because they've talked about it once or twice. Things she would like to have in a relationship. Things that he would love to provide for her. But he can't. He just can't. Everyone would hate him if he even tried. And the one thing worse about feeling like this is being honest with El and having her push him away because of it.
But it's okay. He'll move out for college eventually, and he will meet new people, and he will forget about these feelings. And then he will finally be able to be what El needs: a friend, and nothing more.
