I don’t know what’s wrong

I’m a high school student, have all A’s, my parents are split but i have stepparents for each that I love. 3 younger siblings and one older but I feel so behind with my life. I feel like everyone’s moving up before me and I’m going to end up burned out and an average kid. I want to end it but I feel selfish because people have worse lives than me and are still here, and I would make my family devastated. Maybe it’s just the seasonal depression but I can’t figure out what’s wrong with me and why I’m so ungrateful and selfish for wanting to die