I have no feelings for anyone or anything.
Why do you think you don't have feelings for anything?
I have no interest in discussing this topic
I understand you don't want to discuss this.  However, if you genuinely feel this way you should talk it out with somebody, even if that person isn't me.  Get help!
Nah... I'll be fine since I'm already used to it.
You may be struggling with depression, which can make it hard to even realize that you need help. If you're feeling emotionless toward everyone, you should seek out a professional to talk to.