i'm ok 不好,一般是别人问你are you alright?(当你看起来不舒服时）,你回答i 'm ok.这主要跟语感有关,时态什么的并没有错误,但不应该是正确的说法.
i'm doing ok可以.
i'm doing fine,don't worry about me.
或者是（并不是很好)not really,but i think i can still handle it,thanks for your concern anyway.