How to do certain things in highschool?

I'm a sophomore in highschool and it's sounds kinda weird but I get nervous in the hallways when walking to my next class and stuff. Like for example, I get nervous about how I'm walking and what people are thinking about me and I don't know how to look at people when walking down the hall cuz I get nervous. Like sometimes I ignore my friends when walking and they ignore me. Idk, I don't think of myself as much and I hate that because I overthink too many thing like if this popular kid is sitting next too me, the whole class I'm thinking about what he or she is thinking about me and if I look over there I turn around quickly. This guy in the hallway is sometimes calling me queer and stuff and he thinks he's better than everyone because he always knows what to say in any situation. Since I have low self esteem and low confidence, I make stupid statements and stuff ad the guy just tells me to go die. I feel stupid and retarded because I let it get to me ad I stay quiet. I really want to change my life around but I don't know how. How do I stop caring about what people think and say about me? I feel like ****. I feel like nobody likes me, and I talk low so people keep telling me to speak up. I need serious help! I don't know what to do with my life.