Do you think I'm experiencing anxiety?

I'm 14 and lately i've been so stressed. School is the main thing that stresses me out. I get straight A's usually but I'm always stressing about things like projects, quizzes, tests, and homework. I feel like I'm always going to do bad, even though deep down I know I'm smart, but I always have bad thoughts that I am stupid. I also fight with my mom and sister a lot so i get very stressed from that. Commonly, I end up screaming and hitting things and feeling really stressed. I'm also always stressed about my appearance. i'm short and chubby, so I always stress about my weight and i hate my body. acne also makes me feel stressed even thoguh i dont get it tht bad. Sometimes I also feel stressed for no reason/ very small reasons. Taking part in track meets feels impossible, and for the whole day my heart thumps and my stomach feels like it got punched. Yesterday i had a doctors appoitment and i stressed about it for weeks cuz i was scared to see my BMI and just overall anxious to be examined (in the awkward way!) even though my doctor is a girl and very nice. I was never like this until this year, but lately I feel stressed out wayyy too much. its not tht i want to die, but i even sometimes have suicidal thoughts since i feel like i cant handle anymore stress. i'm going to high school next year my stress is just going to get worse and worse as i age and tht sounds petrifying! do i have an anxiety disorder or am i over-reacting? I'm confused! please help me :/