Thank you for sharing this, I find it encouraging to see that these experiences are shared. I, myself, go through bouts of low self-confidence or self-esteem. For me, one of the most powerful things which has helped me is to be content with my weaknesses and shortcomings -- whether they be skills, emotional responses to situations, or perceived value -- not that I shouldn't work on them, but recognizing that while they are "part of me" they also don't "identify" who I am. Indeed, we each have an inherent value, but we each must figure out what it is that makes us inherently worthy, regardless of our quirks, flaws, or accomplishments (or lack of).
I agree with others that a great way to determine that is through talking with others, either with close friends, family, or counselors; while we each have our own journey, we are not meant to live life alone.