What should I do if I am misunderstood by my good friend and cannot explain it?

If you can't stand up and explain clearly to him, try to use language, including texting, QQ or WeChat. I suggest you explain the whole story in a long paragraph. If you explain it directly in words, it may get darker and darker, and the more confusing the explanation, he may not believe it. It's even possible that you two will fight and send text messages. One advantage is that you can clear your mind. It is very important to express the ins and outs of this matter in your own way, instead of letting him ask questions by the nose, and I suggest you speak first, so that you can take the initiative to let him listen to your thoughts, instead of misunderstanding him.