Tell Me what To believe

Have you ever felt like you know someone, but you feel like you don't know them as much as they know you? So you have to ask them? "How do I know you?" and whatever they tell you..... You have to believe because you don't know if they're lying or not? Well... I've felt that many times. Nearly everyone I meet, I've felt it. I feel hopeless when I ask that stupid question. "How do I know you?" It is quite offensive I must say. What if they were important to you? What if they were your bestest friend and you didn't know? That's a bit insulting i must say.