Ever feel like no one cares about what you say?

Like whenever you say something, someone just says, "Mmhm." or "Yeah." or "Oh." or just "Wow." And then immediately starts a new conversation or comment?
I find it extremely rude, but it happens a lot, with friends and family. So I guess I should just shut my mouth next time I want to say something, because nobody cares.

Pssh. There's this girl at school who barely ever says a word, and when she does, it's like 1% louder than a whisper. (like that one girl on Pitch Perfect? Yeah..) She's more popular than I am and she has way more friends than me. And I'm almost always talking. To tell you the truth, I'm the most awesome, funniest, strongest, and again: most awesome person at my school.

Anyway, off topic, but does anyone ever just like...ignore whatever you just said, and totally start their sentence?

EDIT: Or even just...when you're trying to tell someone something, and nobody will shut up and they're just talking over the top of you. And interrupting too...bugs the heck out of me.

 So what are you saying?

I'm saying that nobody cares when I say something and that I should just keep my mouth shut if that's true. If it seems like I'm overreacting then deal with it, just like I'm 'supposed to do' when people disregard what I say like it's worthless.