Take a story's temperature by studying its tone. Is it hopeful? Cynical? Snarky? Playful?
If we took the narrator’s words at face value, we would believe that her husband is kind and loving, that she really is physically ill, and that women really do get trapped in wallpaper. All of this is questionable at best and mostly dead wrong. This is part of the fun of first person narration—you’re never quite sure if the narrator’s perceptions actually reflect what’s going on. The narrator's tone also clues us in to her character: her uncertainty and hesitation at the start of the story, and her determination towards the end.