我原来只配做你的配角
[wŏ yuán lái zhĭ pèi zuò nĭ de pèi jiăo]
It implies that in the past, I was not considered important enough to be more than a side character compared to being significant or central to the other person. It conveys feelings of regret and self-depreciation, indicating the low status I perceived myself to have in the person's life.