I need help urgently?

i am very insecure with my body i have been living like this for 4 or 3 years i would try on clothes and i would always say in my head you look fat take it off or your fat! you can never hide it ive actully had been made fun of my weight by enemies and brothers and sisters sometimes even my mother does i am not veryy fat but i am in 6th grade and i weight around 110 and 120 pounds why am i insecure about my body at this early age .. do i need help by a professinal? remember im only in 6th grade