After a bicep workout my bicep dont get any bigger?

Hi i'm 14 and i'm 6ft2 i weight 244.4pounds and after a hard bicep workout i don't see any difference during the bicep workout or after. my workout is bicep curls 3sets 10reps per arm 12.5kg , hammer curls 3 sets 10 reps per arm 10kg and barbell 21's 3sets 20kg. ive been weight lifting for 7months after a week i see a difference in my bicep but i dont see a difference straight away in my bicep why is this am i working the bicep to hard or am i doing to little im not sure someone tell me whats happening?