Write a short story metamorphizing sadness as a parasite harming its host. Keep the story between 350 and 400 words while maintaining a heavy and somber tone.
"My heart hurts", I explain to the specialist. "Hm, I am not seeing anything, perhaps it'll go away on its own", the specialist said.

I have been living with this pain. It comes and goes. Some days it's hardly noticeable, and other days it's unbearable. This heavy feeling, like I'm being suffocated, is torturous. I feel this parasite moving inside my body. Some say it's even in my head. I feel invisible and yet entirely exposed. I was aspirational and had dreams. I wanted to achieve things. But this hurt is immensely unwavering. This constriction and heaviness make it more than impossible for me to seriously commit.

Honestly, it's not just a chest parasite. It's an organism growing within, and controlling me. Sometimes, it makes bad decisions for me. It feels like people somehow know and it is something they find upsetting, so I no longer try to socialize. It is indeed internal and eating my insides. At any given time, I think it can explode out of my body. It squeezes my heart, making it beat irregularly and causing phantom heart attacks. These days, I seldom sleep and instead stare blankly. The parasite continues to grow with each passing day.

One day I find myself sitting on my balcony. The cool air and warm sun are too painful to bear. The parasite's grip has gotten stronger and I started crying. I can only think of one way to end this emptiness and pain. Oddly, the parasite seems delighted as well, as if this is what it wanted the entire time. I have gone largely unnoticed my entire life, with no one noticing the parasite, or sympathizing with me during the rare times I disclose the struggle. It is as if not a single person thought that the reason most find me unbearable is not because of them but rather the debilitating pain caused by this parasite. Perhaps this parasite is just a figment of my imagination. In any event, the feelings are real for me even though some said I was losing my mind. I continue to sit and ponder, "What will it take for this parasite to release its grip on me?"