Am i just self conscious are is it something else ?

i always feel like some one is watching me and i always feel like people are talking about me behind my back and i can stop wondering what people are thinking like say if i am walking to a lesson by myself (i don't normally) i always am thinking that everyone else is thinking i am a loner are something like that. i cant stop worrying !! i keep thinking that everyone thinks i am fat are something and talking about me how can i stop worrying and be less self conscious. please don't say it doesn't matter what everyone else thinks cause to me it does ! am i normal does any one else feel like this?? btw i am 14