Wall of sadness

I don't know why I go through time periods when I don't feel like myself. I am emotional, irrational, and completely insane. I don't know how I feel or why I feel the way I do.. It's like I'm consumed by all the terrible emotions imaginable and they just surround me and engulf me like a hurricane. Maybe it's stress, maybe it's hormones, maybe it's something more. What if they're emotions that I've buried deep inside of me that, from time to time, escape and explode into this hot mess. Why does it consume me like this? Why does it become so unbearable that I lay here quietly while the tears stream down my cheeks? Why can't I be strong, fight back these tears and just smile?