The fact Meg didn't pull from his grasp, it made Castiel feel just the slightest bit at ease, because he knew she could have over powered him. He was a human. He was slight and easily stoppable, despite his build being more over her. He knew it took all of her not to fight him on this, even if it was physically not fighting him, because he knew verbally she could do her worst, if she put her mind to it. He'd prepared himself for that, steeled himself against that possibility she would, because he had gotten too close, gotten a confession out of her that he knew was difficult for her to make. If it hadn't been for his realization of his feelings and how he wanted to embrace that, it would have been difficult for him as well.
"Meg," he began with a sigh, because he had no idea what she was saying or why she was saying it. "What wasn't I supposed to know?" He looked at her, his features full of confusion and concern, because it wasn't making all that much sense to him. "I don't understand." His brow knit in confusion, trying to read her features and understand what she was talking about. "Please, just..." he made a motion to the door, grasping for the knob to allow themselves inside and have this conversation not in the hall of his apartment. He thought, if maybe, he could get her inside that maybe this could be sorted out and he wouldn't have that impending fear that she was going to leave again. Leave properly this time, because of the feelings they'd realized.