Her question made Patroclus' stomach drop and he felt his heart skip a beat. When Helen had left him with no explanation, he had honestly expected to be alone forever. It had broken his heart and he had wallowed in self-pity for long enough that his friend Nicholas had gotten annoyed and took it upon himself to set Patroclus up on a date. Then Patroclus had met Roxanna and everything changed.
Now Helen wanted to be with him again, and Patroclus could see this for what it was. Helen, with her heart and head free to choose, had chosen him. Patroclus was just one of her suitors and always second to Achilles on the battlefield, but here and now Helen of Sparta was choosing him. She was not under the control of a love spell or the whims of the gods. And Patroclus was about to break her heart.
"I-" Patroclus let his eyes fall closed and he wished he didn't have to do this. Not right now, after everything she'd already been through tonight. "I love you, Helen," he said honestly, because that much was very true. "And what happened when you left...that wasn't your fault. But I'm in a relationship and I can't- I can't hurt her. I'm sorry. I hate having to hurt you."