The most fundamental reason for not being confident is that I have not received enough respect and encouragement since I was a child. In everyone's eyes, you seem to be a bad student since childhood, so everyone has no special respect for you, let alone trust you, and you lack the necessary fairness. In the long run, you will be rebellious and hostile to others, and you will lack self-confidence.
In fact, you are excellent, really excellent. You just lack everyone's encouragement This kind of encouragement is a great affirmation to you. Only this constant affirmation will gradually enhance your self-confidence. This is the influence of external environment on your self-confidence.
When you can't change the external environment, you have to find a way to change yourself. What you need to do most is to constantly discover your own advantages, such as your poems, your Japanese and so on. Then enlarge your own advantages and give play to your own advantages, so that others will naturally praise you, affirm you and encourage you, and you will naturally have confidence. So, don't always think about chasing your girlfriend now. The more you can't catch up, the more desperate you are and the less confident you are.