Once or twice in a cute, playful way is one thing. However, if a person does this regarding your feelings and thoughts on a regular basis, you need to call a relationship time out and have a serious conversation. Ask why he does this and whether he does this with everyone. Tell him how it makes you feel, and ask him to stop the immature behavior immediately. I suspect that he doesn't do this regarding every opinion or statement you make but tends to do it regarding emotional content. I'd bet he feels uncomfortable expressing feelings or else he just doesn't feel that way about you. Get to the bottom of this, even if it hurts. Even if your discussion leads to a breakup that's better than existing with a shallow emotional connection which is what you have now.