What is the meaning when someone says "I'm Fine"

I'm someone who's  struggling with mental health, The number 1 thing people lie about is they say I'm fine which can be true at some moments but when someone is depressed they say wanna be alone but truthfully they don't in  reality "I'm fine" is a lie so I'm gonna tell u one thing  If u say I'm fine to someone u are rlly saying "I'm not ok"