I don't have low self-esteem, though my therapist says I do. I know I don't because I know that I am a good person, I know that I am worthy (of anything positive..), I know that I am deserving.., etc. If I had low self-esteem I wouldn't feel that way.
But I do have incredibly low self-adequacy (feel like I'm inadequate around others.. especially females of the same age & other peers) & low self-confidence. There's a difference, though, between that & low self-esteem, though there are similarities.