underdeveloped penis

My son is 12 years old and has an extremely small penis ad he is now getting concerned because he has to change and shower for gym class and has noticed that most of the boys are much bigger than him. About a year ago he had called e into the bathroom because he accidently got one of his sisters lon hairs wrapped around it and his father wsn't home to help. At that ime I had noticed that he was just about the sme size now as when he was a toddler. And in the last year it hasn't grown and now I am concerned for him too.  I was wondering if tere is a medical conditin that could cause this or will it improve.  He hasn't let me ask the doctor bacause he is embarressed,  is there anythng I should be doing and should I talkt the doctor about this?

[RockRose]

Has he had regular medical checks?  He should have had a pediatrician check recently where they checked his genitalia.  

[specialmom]

I'm trying to figure out how one of his sister's hairs got wrapped around him.  Oh boy, that sounds unusual.

Well, yes.  Agree with rockrose that you should make an appt. with his pediatrician.  Ours does well checks every year and checks that area quickly.  
good luck