PE Question.

Can a thirteen year old do PE for penis growth? And also, why when I masturbate does my dick seem smaller, it seem like a half a inch smaller, maybe it don't get as hard, but when I go long without it, I measure six inches fully erect, but when I measure my erection when I haven't gone long without it I only see 5.5.

An erection occurs from an increase of blood flow to the existing cells in your penis and the amount of blood flow depends on your level of excitement. Ejaculation relieves that excitement and thus the pressure. It's like pumping up a tire on your car, the more pressure, the larger it gets but when the pressure is relieved it shrivels up.

Masturbation doesn't add any cells rather your penis size comes from your DNA. Exercising your penis will not increase the size any more than exercising your poodle will make him into a St. Bernard. :-)