How To Overcome Persistent Negative Irrational Thoughts?

Hi, I have been struggling with OCD/dark irrational thoughts for years now. They come to me every single day now and there seems to be no way towards stopping them! When I m at school I think everybody hates me/thinks of me sexually/thinks I m weird etc., even when I m at home it s pretty much the same thing every day. I have started challenging these as well but that s not working seeing as I don t believe anything that goes against the negative thoughts.