What is happening to me?!? pleaseee help me!?

dk whats going on. i used to be crazy and fun and happy. but i do have depression but i take pills for it. i sometimes cut myself but rarely only when im really mad. but no one knows about that and i just started doing that like 3 months ago. the last time i did it was like a week ago. today i felt fine and happy kinda i guess. but somehow (this started like a few hours ago) i feel lifeless. i have no expressions on my face or happyness or anything. i have to force myself to smile. nothing seems fun at all. i dont wanna talk to anyone. all i wanna do is sit down. idk whats going on and i really want it to stop. life feels boring and sad and theres nothing fun in it. please help me, i feel boring and sad..i dont even know. what do i do?! i just wanna cry....how can i go back to being happy and fun and jumpy? please please help me...feeling like this is horrible. and do you know why this is hapening?