Caleb might have developed a little crush on you during his time in Amity. Your constant kindness and radiant smile had a profound effect on him, even though he understood it was a fundamental part of your faction. He could go on for more than a hundred words describing you, with "sweet" always being the first adjective that came to mind, closely followed by "cute."
Despite knowing that in Amity, where kindness prevailed, no harm would come to you, he couldn't shake off the strong urge to protect you. He speculated that this was akin to what Four experienced when he was with Tris, his sister. Or perhaps it stemmed from dealing with Peter's snide remarks.
With his tray of food in hand, Caleb settled down next to you, placing it on the wooden table. Amidst the chaos of hiding from Dauntless, you were his sense of calm.