Assuming you are exaggerating just like my teenage nephews and all other teenage boys, 2.5 floppy isn't so bad, just make sure you observe good hygiene. Cleaning under the foreskin helps your penis growth.
my penis size is 9 inches and 2 weeks ago now i have a 9 1/4 inch penis now and i'm 15 years old i also do a lot of exercise
It's difficult to say what is normal for a given age. It depends on what stage of puberty you're in and that can be any between 1 and 5.
Average for an adult male (stage 5) is 5.75 inches erect. Flacid (soft) size is meaningless at any age.