Oh you poor thing! I so much know how you feel and have spent my life feeling like it. So get yourself some help now while you're still young and can change your thought patterns. It sounds like you may have a bit of Social Anxiety. It is very common and lots of people have it to some degree or other especially at your age when how you feel people are perceiving you is so very, very important.
Be clear on one thing. Your thought patterns and your worry about being judged are what are holding you back from being the sort of person you want to be. That is all. You are not a loser and you are not boring and I'm sure you have plenty of things to say but it sounds like your shyness and nervousness and fear of people's bad judgment are holding you back.
Am I right?
You can change how you are feeling, sweetheart. You need to work with someone on it. You don't HAVE to be a wallflower. Some quiet people are happy being quiet and staying home, that's how they like to live, but if you feel that's what you're doing but you want your life to be different then you need to find someone to help you address your anxiety.
Have you discussed how you are feeling with your parents? Would they be supportive to the idea of you getting some therapy?