Feeling under-estimated

I've been feeling as if I'm stuck to one definition- a child.. I am not seen as an influential part of society. That I have to grow up and 'experience things'. People say that I can not give good advice to people, if they are older than me, that I have never felt fear or have been through a lot. No one listens to me. I just needed to say this, and want to know if there is anyone that has experienced this. I also want to know why being a nerd defines you as unpopular or ugly? I just don't understand these things sometimes. So if anyone could explain it, help me. Please

People will always have there own opinions. Just know who you are and be confident in who you are. And don't mind what other people think or say about you. And you define yourself. Labels like nerds or being ugly is in the eye of the beholder. Too sum it up in other words, excuse my language, though just say fuck it. Not everyone will judge you and belittle you.