I got it by simply "not caring" or just internalizing my emotions (Leaving most of what I feel as thoughs instead of actually expressing them). Now I got depression and overthinking and I struggle to express anything.

I do feel stuff, but it takes a VERY strong feeling to make me do something. It sucks, cause sometimes people tell me a joke, or a good news, or something sad, or I am angry about something, and I'm just like :l

If you want to go that way go ahead, but restraining your emotions, specially if you are sensitive, is not going to end well.