Selfish Desire

He's no stranger to the dull, empty ache that comes with losing someone he loves, at the start, when Ms. Blake joined the pack it was difficult, not because her and Derek were hard to look at, it wasn't that at all, but because it was hard to look away from them. It was painfully difficult to not stare at them and wonder how everything about them seemed to be made for the other. Derek made of pure muscle and Ms Blake soft and gentle. The way they both seemed magnetically drawn to each other, and in those such moments, the pack refused to look at him, he wasn't a Werewolf but he could sense the sympathy that came off them in waves. It was those times he was grateful for his little spark that Deaton taught him to hide his emotions with a barrier.
The barrier also stopped the pack from picking up on his pain, the pain that came from the small scars that lined his left hip. He wasn't suicidal, he wouldn't leave his dad alone in the world, but cutting was a comfort, the blood that dripped down his hip reminded him that he was real and that he was alive. He just wanted to feel something other than the loss and emptiness he felt weave about the delicate curves of his too fast beating heart.

And he tries not to be selfish.
Honestly, he really does. He tries to keep the dark swirl of emotions that harbour in his chest from coming out because he's never been good at dealing with his emotions and honestly he just doesn't want anyone to worry over him, he's not worth worrying over.
He tries to be happy for Derek, he truly does, because Derek deserves to be happy to smile and laugh like he laughing now, a joyful sound that sends unexpected sorrow through him. He deserves to have a pack and a fully rebuilt house and one day little grumpy looking children creeping around, he deserves all of it, but he's lost, he always thought his place in the pack was to look after them all, to be the career, the one who makes sure their all fed and have their homework done, but now that position is filled and he's so god-damn stupid.
Fooling himself into believing he was something more.
And god, does that make him angry. The pack is big, 12 members and sometimes it's overwhelming to know that he's the odd man out.
He feels like he's struggling to keep his head above water, tight panicked sensation in his chest, and sometimes it's hard to breathe for minutes at a time, long stretches where he's sure he's drowning on dry land. It's all to much.
Times like that, he hides from the pack breathing harshly into a brown paper bag, his heart beating so fast it's bruising his ribs.

He just doesn't want to be selfish, which is why he'll keep smiling and laughing and pretending that his heart doesn't feel like it's beating anymore.
Everyone finally deserves to be happy, even if he's not and he's okay with that, their happiness is enough. So when Derek comes to him asking advice about wedding rings, because apparently he's the go-to-guy and Derek really is as dense as Scott.
"I'm happy for you," he manages. Stupidly, he adds, "You should hold a pack celebration thingy, I'm sure everyone would enjoy that, including Jennifer." It wrenches him apart to say those words, but he needs to distance himself, to find some way to force himself away.
"Yeah Stiles, that's not a bad idea" Derek says while nodding to himself, "You'll be there early to help, right?"
"Sure" he smiles, maybe it wouldn't have worked anyway, he tells himself as he watches Derek walk away but that doesn't fill up the loss that wells up within him.