No, you certainly do not have to tell your parents.
I do believe, however, that your making a huge deal about rejection and shame if you would tell the parents is just not accurate. If your parents love you and are not very screwed up in the head, they will sympathize. Even if they are dissapointed, any half-normal parent will be concerned and try to help their child in any way possible. That is not rejection, not disowning, and not a shame. It is normal parent-child relations. And though it may be hard for you to imagine what it is like to have kids, I'd ask you to decide what you would like: if your son had a masturbation and porn problem, would you want the boy to open up to you, or to run in fear of shame and horror and, instead, keep it a secret and 'keep fighting'? Again - not a reason to tell! - but just something to think about.
Furthemore, a father (or mother) who has a porn, masturbation, or sex problem will often only open up about their own garbage as a result of their child opening up about it! I have seen this happen.
The only point I always share is this: opening up to safe understanding people is key in making any real change, at all. Somebody! Hiding it from parents is really just a way to hide it from everyone - and opening up about it here while hiding behind a username, is not really opening up enough. The fact that 'to tell or not to tell?' is such a big deal, demonstrates the need to tell somebody - and 'telling' on this virtual forum is just 'virtual telling...' That is what my heart tells me here. Sorry if I am way off... again.
Hey. Fake change we all have plenty experience with, right? I know I do! Maybe you feel the need for real change, and instinctively know that it will only, only come from real connections. The porn is all about fake connections - fantasy connections. Gevalt. This is so key to me in my own recovery. So I share it here and everywhere.
Hiding and lying is key in keeping on doing everything we have always been doing, and got us in this mess in the first place.