I've had the problem since my childhood. I hated expressing my emotions. When something great happend it was like
[my relatives]: You aren't happy? O____o
[me]: I am.

And now I am like "why people go with this emotional **** all the time". I've got headaches when feel strong emotions, no matter if they're negative or positive. I acknowledge that probably emotions are very important in my life and I have problems partly because I can't live them through properly but most of the time I'm just indifferent and I don't even know how to describe my mood not using the most popular adjectives like "happy" or "sad" (in fact these are extremals and maybe that's the problem, I can't describe usual states). It's easier when I've got a list of adjectives and I can just choose something.