Kaliope's advice to just release the judgment fully covers the shame/guilt issue and should be easy to implement.

On keeping it a secret:

- while I do not watch porn, I know it is a very big industry, and, therefore, lots of people watch it. Your parents and friends, likely enough, are among those people. You are overestimating the chances that they will think of you differently (grossly overestimating); however, you are entitled to privacy and you might consider your watching porn a private activity. All you need to do is change the language that you use in your mind to conceptualize what you are doing: remove "secret" and insert "private" instead.

FROM:I keep watching porn a secret
TO: porn watching is something I do in private and I do not talk to others about some of my private activities.

Hopefully this will solve it.