Little of what you wrote leads me to believe that you have a narcissistic personality disorder (NPD) but a short letter over the Internet would not be sufficient for an accurate diagnosis. I know that you were not requesting a diagnosis but I just wanted to be clear that you could have NPD even though it does not seem like it from your letter.
You mentioned that you do not like being criticized. You also said that you find justifications for the criticism you receive and believe that those who are critical of you are wrong and you are correct. Those may be symptoms of NPD but there are people who do not like being criticized and do not have NPD.
Being criticized, for some people, is emotionally painful. This is primarily because they take the criticism from others very personally. Some people confuse a criticism of their actions with a criticism of their character. They seem to equate criticism with the idea that they are a bad person. Thus when they are criticized it’s insulting and a “blow” to their ego and overall self-image. This may be how you are taking the criticism you have received.
It could also be that you are correct and the others who have criticized you are wrong. In this case, your justifications would be correct.
If you are hypersensitive to criticism and you judge that the criticism is justified, then your goal would be to try to not take it so personally. The challenge would be realizing that others can be critical of your actions but that does not mean they think you are fundamentally an inferior or bad person.
You also mentioned you are engaged in teaching in China. Could it be that the cultural differences account for the criticism (i.e. your messages are misinterpreted or vice versa)?
In summation, there are several possible explanations for this problem. You are misinterpreting the criticism that you are receiving and you are hypersensitive to being criticized or you are being misinterpreted and the criticism that you are receiving is not warranted. Whether or not you have NPD is something you will have to have assessed by a trained mental health professional.
As for whether or not you should seek help, you should if you feel that the problem you wrote about continues to bother you or if you having difficulty knowing if the criticism is warranted. An objective opinion could be very helpful. You should also seek help if you find that this problem inhibits your psychological growth and causes you emotional distress. Thanks for your question.