Emotional relapse

Today, I broke down emotionally for the first time in about two - three weeks. I cried over something so little. My dog Annabelle didn’t even let me cry into her like she usually does. I wanted to pull my hair out, lay on the floor, I wanted to scream. I was alone and I just feel like crap. I made my best friend feel bad about something, not meaning to. I hated myself in that moment. I’ve been dealing with my meantal illness since I was eleven or twelve, no body knows and it’s a few years later. Why am I such a bad personality? Why do I act like this? Why did I cry over something so small?