Why is it that the things that make me happy also are the things that make me sad?

I think the title of the post says it all. I just don't understand why that has to be. It's not fair, really. What makes me happy? Sitting in the kitchen on a cold wintry day, drinking a cup of tea, talking with friends and eating warm cookies used to make me happy. Not so anymore. Those cookies started a binge session that just finished recently. Ugh, not fair. Sleeping made me happy, now it's an escape from reality, and when i wake up i just want to eat. My birthday used to be something i look forward to, now it's just something i dread. I feel like life's little joys have been snatched away from me, and i don't know how to find them again. And I feel like something's missing. I try to fill the void with alcohol, people and occasionally food, but it's not working. What is happy? What is fun? Some days I don't remember anymore.