He knew that he wasn't being very subtle, but he needed to know. He had to be sure that this was nothing to do with her sire bond to him. At the heart of it, Damon simply desired that what Elena felt for him be real. He couldn't stand the idea that what she felt for him might be out of her own control and against her will. She needed to be making the choice.
She cupped his cheeks and he knew that if he still had a heartbeat, it would be racing right now. It was crazy to him that he had lived 170 years and Elena could reduce him to feeling like a teenage boy at this time.
She took the glass for him and he assumed in that moment she was about to take a drink, and thus proving that she was still sired to him, and he felt flat, believing that this notion to move in with him was simply a desire to make him happy.
But she didn't take a drink, instead setting the glass down and turning back to him and a flicker of hope started to rise inside of him. What if... all of this was real. She would have drank if she was still sired to him.
His hands fell to rest on her hips and for the first time in his life, someone had told him that they loved him and truly meant it. A smile started to creep across his lips and he leaned his head up to press a deep and powerful kiss to her lips. "I love you too," he murmured against her lips.
It felt like this massive cloud of panic and doubt had been lifted from him. No longer sired and still she chose him. Not a single thing else but Elena mattered to him right now. The world around them could fall apart and he would not care. Because finally, he had gotten the girl.