I don't get it, why?

Hi. It's me. Sorry for the incomplete introduction in my first blog post (April 25, 2017). Maybe one of these days I'll edit it and make it more informative. Anyway, I'm about to share some of my thoughts, things or happenings in my life these past few days, weeks, or months? I don't know. I'm not sure.

  Most of the time, people see me as a happy, jolly, or bubbly girl. Even my eyes smile too whenever I'm laughing or smiling. I crack corny jokes, I sing at the top of my lungs, and I tell stories endlessly, have a lot of friends, doing good with my studies and everything. I'm also the type of girl that doesn't want the people around her feeling sad or worried. Despite these things, sometimes I will see myself feeling confused, bad, alone, and all the negative emotions combined. Well, it is completely normal especially during adolescence period, but as I grow older these emotions are getting worse. It's like a big black shadow crawling and getting inside me and destroying all the happiness I have. I don't get it. All of a sudden, I feel sad, horrible, just so bad. Worst is alone. Some people are telling me to be okay or to feel good about myself and everything in between. I tried to, I always try to but the pain is bigger. I don't get it, why?
Sometimes I even see myself crying at night asking why am I suffering this way. Why should I feel the pain of the things that's already done? The pain of having a broken family, the pain of people betraying me, the pain of someone leaving me. Why? These things that happened to me already happened a long time ago, the latest was about 3 yrs ago. And I already forget about it all, still, fate finds it's way to appear in my mind and wave a hand at me. And then I'll wake up worse in the morning and when I jump out of the house I'll be fine again, then in the evening, I'll be that problematic-nothing-to-say-nothing-to-react-girl again. And the cycle goes on and on each and every day.

From a positive person during the day to a weak one during the night. Again, I don't get it. All I want is for the pain to stop.

I actually have noticed that even the small things can make me sad. I will not be specific but it does. Maybe it's just me overthinking or something. As I have already mentioned, this shadow is making me weak and fragile. It's getting worse. I don't get it, why?