It's up to you in this fic! Still, I wrote it thinking the baby is Harry's - but it was a mistake. Harry had been cheating with Draco but planned to extricate himself from the relationship. He was still sleeping with Ginny though and she got pregnant, and he felt he couldn't abandon her, especially since he'd lose Ron and the other Weasleys. So just when he thought he'd escape and finally make the break, he was stuck.