I have this headcanon that Draco would struggle with saying “I love you”
When he was young he never really said it, it wasn’t the “done thing” between pureblood families, especially not ones headed by Lucius, where it was all polite handshakes and the only way to show affection was through obedience and respect.
And then moving on to Slytherin house at Hogwarts, it wasn’t much different. Most of the students also having been raised similarly. Expressing ones emotions like that was a sign of weakness.
But then Harry Potter comes along, and by the time they’re in a relationship, Draco’s sure he’s already been in love for years. He wants to say it every time Harry smiles at him, and every time Harry does one of his irritating Harry-ish habits, and every time Harry whispers it to him like a promise.
He knows Harry doesn’t mind him not saying it, that Harry understands how much he means to Draco, but it isn’t the point.
The first time he says it, it’s shaky and whispered and murmured against Harry’s lips as they kiss on a lazy Sunday morning in bed. It’s the smile Harry gives him, the smile like Draco is the best thing in existence, like he’s the only thing that matters, that makes Draco say it again.
The more he says it- when Harry’s laughing at the Prophet, when he’s making them coffee, when he’s moving above Draco in bed- the more he wants to shout it from the rooftops.
Because he’s in love with Harry Potter and he’s never been happier, and he’d say “I love you” a thousand times if just to see Harry smile as he whispers it back.