My 4-month old squirms all the time when breastfeeding. She wriggles, flails her arms and legs (sometimes quite violently), and rubs at her face. I'm finding it difficult to keep her latched on. Why is she doing this and should I try to pin her arms down when nursing?

Try talking or singing to her. Tell her about your day, or about her day from your perspective. Read her a story. The sound of your voice may help calm her down. Or try feeding in the quiet and dark room. All these may help create a more "conducive" environment to help her relax.