我爱你你怎么不知道
[wŏ ài nĭ nĭ zĕn me bù zhī dào]
Directly translating as 'I love you, why don't you know it', it expresses frustration and perhaps helplessness. There is love and expectation that the other party understands or returns these sentiments without being told, conveying the idea that loving actions and emotions should be perceptible enough without verbalizing them.