Caring what others think

I worry about what other people think of me so much. (I'm a 16 year old girl)
I'm starting my junior year of high school in 2 weeks and I'm pretty nervous. I built up all this confidence and was ready to take on the school year and be cool and not care what everyone else had to say.
But today I had to go to the school building for something and I suddenly felt this nervous feeling as soon as I got on school grounds. School wasn't even going on and I still felt nervous. I kept thinking "What if someone sees me?" "I'm such a LOSER."
Now I'm terrified about going on the first day of school and not having any friends in my classes. I worry about friends a great deal too.

I just don't want to care what people think of me and have confidence and love myself.

I'm a guy going into senior year and I am nervous like you. Throughout my life I have been bullied and trouble making friends. But my junior I just told myself that who cares what people think of you. You will be off to college and done with people. You will make friends just by being yourself. Don't ever pretend to be someone your not. Your not a loser. Never think you are. I find writing down or in poetry your feelings really helps leaving those negatives thoughts on paper.

You are you. Don't let anybody affect what you think and what you do. Being yourself is important~ I have the same problem as you, but I find that changing my mindset helps. I used to get nervous for first day of schools, and whenever I'm outside, I get nervous for no reason too, I'm afraid that peoples are looking at my every action. But in actual fact, they are not. I still feel the same way now, but I find that ignoring them makes me feel better. My dear, fear is not to be feared, it's to be challenged! Challenge your fears and overcome them, because they will never never ever get into your life and affect you. All the best~

I used to care too much about what other people thought of me. However, I no longer do, especially since I think most people like me.

The reality is that trying to have everyone like you would be an fine goal if it were a realistic goal. But it isn't realistic. Therefore, there is no point trying to get everyone to like you and respect you as well.