I just don't like to leave a mess. I know my parents are gonna find out if I leave just a slight mess. When I have it held in, I would put my pants back on, still holding it, and go to the toilet to let it out there.
When I decide not to hold it, I would always sneak about 4 pieces of toilet paper before doing so. 2 for catching it and 2 for wiping my snake.
Wtf do your parents think you're an angelic innocent little boy or something? Your profile says you're 16, they know you do it whether they find evidence (why would they specifically go looking for it?) of it or not.
Pretty sure 'holding it in' like that isn't healthy