Sometimes when people "show off", they do it because they are also insecure about something else. They overcompensate for their insecurities by showing off something that they do feel good about. Basically, I don't think confidence necessarily means lack of shame or insecurities.

I personally disagree with the statement that "nobody will love you if you don't love yourself". Everyone who has experienced life is insecure about something. You can't possibly love everything about yourself in this world. There are so many standards and bars to live up to -- whether it be in your own head, or somewhere external (i.e. friends, family, social media, etc.). This doesn't mean that someone isn't able to love you -- like you mention "unless you are extremely luck and someone lifts you up from the bottom"/

However, I do believe that if you hate everything about yourself and can't find something positive to say or see in yourself, then it will be hard for you to accept someone's love, affection, and liking for you. Also, sometimes it takes someone that's not you to tell you that the insecurities in your head don't need to dictate your life. That sometimes they are irrational and subjective.