i suspect the non-feeling is more a survival instinct when facing traumatic events and information. we do become de-sensitized. many of us are afraid of our anger......because that isn't how "nice people" behave. and angry people upset others. and nice people don't do that either.
i think from your shares here that one thought you have clung to is that you are ALL he has. that supports your internal belief that he is really a little boy lost. and like it or not, that helps support the "savior/martyr" role you have assigned yourself.
Yeah, I'm with Anvil. This stuff is traumatic, and we tend to shut off UNTIL we can deal with it all. Maybe that's a couple years down the road for you....but you are going to have to deal with it at some point, and it's not going to be easy. And you don't need to be embarrassed here...don't think many of us haven't had similar experience.
Please, PLEASE tell your therapist (they have heard worse...I PROMISE.) We are human, everybody makes mistakes. Guilt and shame and keeping secrets keeps US sick.