我爱你时,你才闪耀,我不爱你时,你什么都不是!这么说对么?

原句中有一个语法上 时态一致性的错误
后半句 but you are nothing when I didn't love you
的are 和 didn't 时态冲突

就算都发生了你也可以用一般现在时，因为这句对任何人在任何时候都应该算是普遍真理啊，而且 you are nothing for me这个事实是会一直存在，只要你不爱她了，You are nothing 这件事就会一直持续下去，所以后半句最好就用一般现在时
如果前半句还是想用过去时的话，就不要用逗号连接两个句子了，用句号隔开
When I loved you, you were shining as a star.But you are nothing now as I don't love you any more.

楼上那个You are shinny when I love you, but you are nothing when I don't. 的 说法不错，但是有个致命错误。。shinny..不表示闪耀，而是动词，表示爬上爬下

You were shining when I loved you ,but you are nothing when I didn't love you !

都应该用现在时，因为表明某种情况下，而并不一定是真的发生了。

最简单轻松的说法
You are shinny when I love you, but you are nothing when I don't.

前面对，后面应该是but you will be nothing when i'm not loving you

You were shining when I loved you ,but you are nothing when I don't.

前半句确定是完成时喽：）
后半句要用现代时就前后都用好了， 而且不要重复love了，很别扭～