Why is everything so bad now?

I spend every moment these days trying to grasp onto the last memory I had of what having no worries felt like, where my biggest problem was wondering if I'd ever grow taller or if my crush would ever like me back. These days, there's so much more. There's this sour aching feeling in my chest that creeps up on me every once in a while, it pains of loneliness and hurt. And I don't like it. I don't like how things have become or who I've grown to be. A side of me tells myself it's growth, it's learning, it's figuring out who you're supposed to be. Another part of me is telling myself that growing up shouldn't be this hard, it isn't supposed to be filled with ethereal temperamental happiness and scarlet self loathe. It shouldn't be feeling a void inside of you or constantly pulling down your sleeves. Why is it that I feel so down all the time?