"It appears as if my presence is upsetting to you, so I was uncertain of whether or not you wished me to leave." Castiel wanted to frown at the idea of her asking him to leave, because he didn't want to. He wanted to remain here with her, despite how he wasn't sure of how to carry himself with her. Things had strangely become even more intimate between them both, thanks to her taking care of him and his watching over her as she slept, when he was in possession of her power. It was difficult trying to work it all out, on top of trying to work out being a human and experiencing different things for the first time as a human rather than an angel.
That thin line played along his lips when she made mention of how he was the only one who cared if she lived or died here, because it was something that made his heart constrict and he knew it wasn't a heart attack. He wasn't entirely familiar with how one felt, but he knew it couldn't be because it lacked in other symptoms. But the idea of Meg dying here, it was not something that sat right with him. It was why he'd be firm with the Winchesters and anyone when it came to her safety and how he was going to protect her at whatever cost. He knew she could do that on her own, but he refused to watch something happen to her.
When she posed the question of why he didn't take what he wanted, because they both knew he wanted her, something that made him look down for a moment, a feeling of being shy washed over him when he knew she was aware. She'd probably been aware from the moment she pulled him over by his tie.
"Because I've never been faced with that choice before." It was truthful, honest, everything he could be in a moment like this. He never had the opportunity to give into earthly desires, at least not when he was himself, that was. Emmanuel had been married, so it made sense that he was able to enjoy that with his wife. But it was not his own experience, in an overly complicated way.
"I...do want to move furniture with you. Like the pizza man and the baby sitter. But I am also newly human." Meaning, he was trying to adjust to that. Everything about him was different now, meaning his limits he could push his body to had gone down severely.