Okay, legit, if you're sensitive to self harm, passive suicidal ideation, and/or deep depressive thoughts, please consider not reading this. Look after yourselves, people.
That aside, if you're alright with the themes of this story, buckle up and enjoy (?)

He couldn't stand it. Every moment from when he opened his eyes to start the day and crash down in the wee hours to sleep away the few hours he could have used for homework, he was overwhelmed. School, ghost fighting, Vlad, the jocks at school, and even home, with his parents making weapons designed to hurt ghosts (they don't know, don't be so critical) disoriented him. He needed reality, control. A distraction. A wakeup call. That was the start of the habit. He'd told himself he would be able to control it no issue; just a few times isolated from each other that he was certain he was okay. It was a spiral. It started with the idea that, hey, ghost fights made him feel less dead sometimes. Maybe he could the same without almost getting blasted to pieces. His eyes had landed on an abandoned scalpel that his parents, the irresponsible scientists they were, had left out. Tentatively, he made a small nick on his inner wrist and was fascinated that the pink mark from the sharp object made him feel calm. He stole the scalpel and feigned innocence when his mom stressed about the whereabouts of the instrument.

That night he'd put the scalpel to his shoulder, careful not to press too hard, and dragged it across his skin. The sting hurt terribly, but that felt nice in its own way. He'd used a wad of tissue to stop the bleeding and flushed it down the toilet. Just a few now and then, he'd promised himself. No more than two or three on his shoulder until it was really bad. And yet, here he was, over fifty marks and scabs and scars on his upper arms. Maybe a button down in the name of "mixing it up" could cover this mistake up. Danny squeezed his eye shut as the dark thoughts came back to his head. It was worse than Spectra. At least then he could blame her. But this was just him. Petty, lanky Daniel Fenton. Forgettable. No one would mind if he died, but he had no doubt Jazz would be missed. Who knows, maybe people will be happy if he-

He snapped back to reality and blinked slowly. He tried to move his hands to his head so he could comb through his hair but his arm stinged and he hissed, grabbing it and adding more tissue. With the pain waking him up, he shook his head to get rid rid of that pesky little question. Would he be missed?

Life was a blur and, with the lack of coordination from exhaustion that had never been so bad before, the other ghosts were harder to beat. Sometimes, he thought about asking for help on… the ghost fights. Nothing else. He was okay, just fine, a little overwhelmed. As long as he had a release, he would be okay. Not that he should be worrying about it, since that wasn't a problem. Soon enough, even the Box Ghost was hard to beat sometimes, when he was wrapped up in his thoughts. Those battle usually had their failures wrap around his head tightly until he reached for the scalpel and it would be okay.

So maybe half sleeves and jackets had taken over his wardrobe. So maybe gym was uncomfortable for several reasons. It was okay. (It had to be okay, because there was no way he needed help, it would be petty.) Mr. Lancer stopped giving him extensions and his grades dropped further. Why was he so tired and hopeless? The questions didn't matter. He had to focus. He reached for the scalpel, and it was there. A constant.

Danny breathed out slowly. He needed help. Not just with ghost fights, or school, or even the scalpel (which, yes, was a problem, he realized). He couldn't stop thinking terrible things, thoughts taped to his head on loop. Thoughts that made Spectra seem genuinely therapeutic in comparison. They were most likely lies, he knew, but deep down he felt them to be truths. He wasn't loved, or cared for, no one would blink an eye if something were to happen to him. He was about to knock on his sister's door when he lost his nerve and started walking away. Another day.

The ghost fights were dull and grey, the days were a haze and he remembered nothing for long stretches of time. It was hard to concentrate when the weight on his chest just wouldn't go away and he'd feel like crying whilst being too apathetic to show emotion on his face. The other ghosts were backing off slowly. Danny didn't let himself believe that even the nicer ghosts were caring for him; it just wasn't fun to fight him.

The scalpel was essentially a part of putting one foot in front of the other, aside from meaningless things he felt silly for caring about: seeing Tucker reach level 16 on DOOM, for example. Or trying to pass the test next week. Cujo paying him a visit. The nights kept on passing. The scalpel was essentially like a magnet sticking to his skin when he couldn't think properly enough to stop himself.

At some point they got deeper. He supposed that maybe the garbled static in his brain was making it harder to reach that same clarity.

Spectra found him one day, and she wrapped her hands on his shoulders and whispered to him until he just slumped, stupefied. Jazz found the two and sucked Spectra into the thermos, muttering an insult into the thermos before she closed it. She ran to her brother. He blinked a few times before crying his eyes out and hugging Jazz tightly. She let him.

An eternity later he told her. She looked distraught before hugging him tightly, gently touching his arms and asking questions about his feelings.

"Are you thinking or feeling like you'd be better off dead?" She asked. He looked away and didn't respond. "Oh, Danny…"

He wasn't in school for a week when his parents found out. He shamefully tossed the scalpel on the table and decided to sleep on the couch for the sake of his family's peace of mind. Therapy was definitely on the list of things that would be changing for him. He sighed. It was for the best. Maybe the stupid scalpel did something good after all. (The scalpel did nothing and it was all him, but he felt better thinking about it that way. Giving himself some slack.)

One foot in front of the other; it'll be okay.