There is some good advice in the thread. I will add one point, apply yourself more. Without engaging in a task and completing it, you won't feel confident about it. You need engagement regularly to stimulate your worth. You might also need others to acknowledge it which can be hard. I know I personally stopped believing any praise or acknowledgement I was given irl. I didn't compare myself to others per se but I was extremely stuck on the idea that every attempt of mine should produce better results than the previous. People didn't notice my critical flaws then how can they be good at praise.

As for any specific thing you could try, find something that is interesting to you. Find a small internet community about it and engage. Learn from them and tell them what you know. Build trust, then try to move it to offline meetup or places. Someone you trust and idolize telling you how valuable you are as a person is a great booster.