Well, he's been cursed by the Dragon Council to remain in a humanoid form because he came to the defense of a hen (female dragon) who was being attacked by a male. Dragon society is misogynistic, so this was a crime. :(

After he rescued Anya from the mess she'd fallen into, and she gifted him with the ability to return to his dragon form one day every year, he's been very careful not to press her in any way.

Shorter Version: He's head over heels in love with her, but is too damned honorable to act on it unless she hits him with a sledgehammer. ;p