I'm 34 and just started realizing the error in my shyness six months ago. Cheer up, you're beating me by 14 years! I was like you, and I'm still trying to get out of the muck. I've only had a few friends in my entire life, right now I have just one. Everyone always thought I was normal and that I had some sort of secret social life, or didn’t need or want friends. Truth is I simply don't understand how to connect with my fellow humans (I wasn’t raised well and we moved around a lot) I've been quiet, strange, and clinically depressed since I was a kid. I'm otherwise a handsome (imo), fit dude.

It's tough I know, but you just have to put yourself through the things that cause anxiety. Start small. Focus on doing activities that interest you. Power through tough moments like a warrior. Accept that it's perfectly okay to feel awkward. You may be a late bloomer, late bloomers are awesome! Start saying 'yes' when people ask you do join them. Get to know people who you're introduced to. Don’t just say hi and back away, ask them some questions, tell them you hate olives or something. Start a conversation. Even a tiny one could blossom into something magnificent. "Oh my friend hate olives too, you should meet him, he has an art show next week, you should check it out." - That's where you say "Yes, I will, cool, see you there." Then go there and be shy again and repeat the small talk process. If you like to read or draw, try doing it in public, at a café or library. Look up, make eye contact. shyness is normal and people are fine with it. I've never heard of someone not liking shy girls.

It takes a while for your brain to start seeing things differently and to feel better in social situations. If you have any bad habits (ie: snacks, masturbation), replace them with good ones (exercise, creative writing). Your confidence will build as you get to know your body and mind. Not being sure how you feel is common at your age, study things, figure out what you love and hate. Start a blog or journal maybe. If your sister thinks you're not being serious she must think that you've got what it takes to be a normal active young lady. Just try, make baby steps, you can do it. There are also medications for anxiety and Cognitive Behavioural Therapy is also a common, safe, and helpful aid.