Hi there,
After reading your post, I was immediately reminded of this bit I came across years previously. It's about how the writer understands the dynamic of the addicted mind.
Grieving
Not saying you're an addict

I just feel this dynamic might be applicable to anyone who 'has experienced many overwhelming sorrows without being able or without being allowed to process them. The pain that we experience is greatly due to preventing ourselves from feeling these sorrows.'
Does this sound like it could be you? You say you try to pretend happiness - is this something you've been doing for a long time? Maybe it's time to start talking about some of the things that might be bothering you. PsychCentral is a good platform for that, or if you have a trusted friend you could talk to, it'd probably help you greatly!