Hey there!
Puberty and hormones are probably contributors! They can make emotions much more extreme. Your parents are also right in that a LOT of people go through this kind of thing, and just about everybody has SOME form of issue(s) in the teenage years. Being grateful for what you DO have is always great, too...but that doesn't mean to ignore your issues! I'm really sorry that you're having to go through this, and I hope things get better. Let me know if I can do anything