Harry is used to the universe toying with him and being an overall bitch. He's used to sudden deaths (it's inevitable), false accusations (he doesn't get paid enough for it), and assassination attempts by the DADA teacher (really, where was the originality?). So watching Draco Malfoy revealing that they were in a relationship in the most Malfoy way possible? Please. He knows.

Why he was running was a mystery even to him (that was wrong he knew precisely why. He wanted to see him). But, a sense of desperation clung to him sinking its teeth into him like a vampire would when draining the blood and life of its victim (He knows. He's seen it). Or The war is finally over and Harry's tryna find his most precious person while having epiphanies.