Should be obvious?
They know they're not perfect, but they think they're getting better
Someone else (probably an ex) said they were better than they were, the singer was too deep in depression or whatever to see it was true. But now, as they're getting better, they're starting to see their good traits

>>29594021
It means he's an angsty faggot who lives to mediocre 3rd wave emo

>>29594021
I shouldn't act as if my guess is necessarily the right one, but this is my interpretation:

>And I am flawed
He has personal issues that restrain his relationships towards others
>But I am cleaning up so well
He has successfully worked to get rid of his bad habits that always made him look down upon himself
>I am seeing in me now the things you swore you saw yourself
Because of his successful self improvement, he no longer looks down upon himself like he used to. With all those things he hated about himself now gone, he can instead see his good traits shine without being covered up behind all the bad ones. However, when his special other brought up his good traits in the past, he couldn't see them himself and hence never believed her back then.

>>29594021
He means you should kill yourself for being a gigantic faggot and stop posting tumblr tier lyrics