Obi-Wan could feel many things in that instant. Self-consciousness, at having laid himself bare to her, when he's only just come to terms with how he's feeling, himself. Mortification, that she's pulling away, potentially rejecting him, even if it is temporary, while she comes to grips with what he's implying.

In the end, however, he winds up ducking his head to hide a smile, trying very hard not to start laughing - sure that she would think he was laughing at her, which is definitely not the case. No, he's laughing at the situation he's found himself in, and how unprepared both of them are to deal with it.

Obi-Wan stands as well, much more slowly, turning toward her as she moves to, ostensibly, make him some tea. "Padmé..." He waits until she turns toward him, and for a brief moment, just looks at her. "I love you." He says it simply, and clearly with no expectations for her to return the sentiment. "I feel you should know, partly because I'm not sure how well I could hide it from you, if I had to try. And partly, because I never want you to question my actions, or the motives behind them, where they concern you. I want only for you to be happy. And if my feelings make you uncomfortable..." He looks a little uncomfortable himself, but forges on. "Well. We can figure something out. We can annul the marriage and you can find someone else to guard you."

Which is absolutely the last thing he wants, but Obi-Wan is used to sacrificing his own happiness for the sake of peace, and he would never want Padmé to be trapped in a situation that makes her uncomfortable.