Anal sex is something that if not done right then yes will hurt. And It also is based upon the person getting the who is getting penetrated's mind set. If they dont want to do it, it wont be pleasureable, or If someone is focused on having an Orgasm throught the means of anal sex then it will not happen because of diff. pressure made by these thoughts. A way to make anal more pleasurable is to, perhaps in the shower, Insert your finger everyday. And to make sure you have enough fiber in your diet.
I would suggest that you. dont do this because of the many STD's you can get by it, gonorrhea, syphillis, herpes. And it is possible to conatract the Aids virus, If a tear in the rectal tissue accures and semen is released then the infected semen can get into your blood releasing the Virus. Again I warn against.
I really dont think that this has to do with puberty but I will leave that up to the mod of this forum.