pls help

any advice on coping with overthinking negative irrational thoughts? sometimes i feel like two people are living in my head. the one is nice and positive and the other wants to see me self destruct. some days I cry so much that I cant breathe. why cant i be normal and happy. sometimes i cant remember the last time i was happy or just feeling good. sometimes i feel like happiness is just an illusion. sometimes i dont understand why and what is life. i wish i was normal. i feel like i am too sensitive.