My biceps are big in only one spot?

i have been doing intense workouts my whole upper body and abs with cardio and that junk. when i flex my biceps like you would normally do they are big and peaky, but when i put my arm down my whole arm is thin and scrawny. my shoulder and the rest of my arm is pretty much one part. i am not that skinny, i and 5'7 1/2 and i am 14 years old. i weigh 130 pounds. help please