After Carmella sleeps with A.J's teacher, she grabs a gun and places it under the pillow after staring at Tony's picture. My question is, does she place it there out of fear that If Tony finds out, he'll hurt her, or is it because there is no more security in the house that Tony brings?

The hero and the coward both feel the same thing, but the hero uses his fear, projects it onto his opponent, while the coward runs. It's the same thing, fear, but it's what you do with it that matters. Cus D'Amato