tips for better confidence

I’ve always had super low self-esteem mainly because I always felt compared too especially when it came to my parents, so every time I would do something better I would then compare myself to my siblings. I recently started to feel a little bit of confidence, and more carefree. Until I told my best friend who I like, I love the girl but she’s a blabber mouth. And today I found out I sit right behind him (like literally less than a feet in between us) and I keep getting panic attacks for what she is going to say, I told her that I like someone who goes to a different school. I have zero confidence when I talk to boys, I like to look at peoples eyes when I talk to people but I find it awkward when talking to any boy, and I always say something stupid, so any tips?