To express or not to express

Most of the times, I think about doing something, saying something to anyone, asking for some help, sharing something or telling how I really feel, but always end up thinking- 'it won't really matter, nobody cares, so just keep it to yourself'.
This decisions sometimes payoff, while at others it makes me curse the time I thought about it. I just keep wondering whether it is right or wrong to be an introvert, but never do I get an answer, neither can I stop being one.
This situation mostly misleads people, especially my friends (and some of the family members), and they end up thinking that I do not have any emotion for them, am not interested in anything that they say or do, and nothing matters to me.
Actuality, however, is exactly the opposite.
I do care, I do love, I do feel, the problem is- I just don't know how to express or not to express.
Whenever I am about to say it all out, something stops me from inside and tells me that there isn't any need to put your feelings on display.
So, I always end up keeping it to myself and then spend hours and hours wondering what would have happened had I said it out. Would it have made anyone happy? Or it would have sounded like those formal statements uttered by everyone around. There is no solution whatsoever, and I guess I would remain the same for the rest of my life.

However, no one knows what would be more soothing at the end of it- the unsaid words or all the things well expressed ...