Living, Loving, and Learning, by Lumos_Maitre

"What the hell happened?" she asked him quietly, her voice trembling, betraying the anger she still tried to hold on to. "What changed?"
"Our relationship had an expiration date," he said, his tone matter-of-fact, like he had already come to terms with it, like he had already given up.
OR
Hermione Granger's life takes an unexpected turn when she discovers, through the Daily Prophet, that Draco Malfoy—her long-time partner—is about to marry another woman. Shocked and heartbroken, Hermione tries to make sense of the sudden end to their relationship.

Just two days later, her world is turned upside down again when she finds out she’s pregnant with Draco’s child.