The best answer to this question is “I am happy”. The second best answer is “I’m not happy now, but I soon will be”. If neither of these answers occurred to you, then you should probably ponder the question a little more.
In order to find the root of your unhappiness, you have to figure out what exactly you are. If you figure out what you are, then you will be happy. What you are is exactly what you are experiencing right now. You are a computer screen with words on it, perhaps with music in the background. You are that. So what is there to be unhappy about?
If you have a situation that is making you unhappy, then you are stuck. To unstick yourself, you have to breathe. Breathe in and ask yourself, “What am I?” Breathe out. Do this once and you are present. If you are still unhappy do it again.
Your unhappiness is related to something from either the past or future that is tainting your mind. Mostly, it is tainting your idea of what you are. You are not living up to your expectations of yourself. This is a problem of both your expectations and of course your Self. When you experience your True Self, you will no longer have expectations, you will have only actions. You will be happy.