Have you ever felt as if you can't be 100% honest with people? Like your hiding something?

Being in school is very stressful for everyone at my age.Its all about ’‘popularity’’ or ’‘fitting in’’.I personally don’t like the ways people categorize others.It’s just a label.I have a very good group of friends who have been there for me from day 1 and im very thankful for them but sometimes i feel as if there are some things that I can’t tell them.I mean,i tell them everything and they know all my secrets and everything about me but sometimes I’m worried that my opinion on things will affect them or maybe they wouldn’t understand.They’re very great friends and I couldn’t ask for another group of friends at all,they’re the best in the world.The thing is,I wonder if maybe i should just suck it up and tell them my view on things like popularity or relationships or even some honest responses to their problems but i dont know,i guess it’s complicated.Have you ever felt this way or is it just me?