Coming out is different for everyone. You family, your friends and your colleagues are unique to you, and only you can decide when and how to share this information with them.
For what it's worth, here are a few random thoughts:
1. Coming out is a one way street. Once you're out, you're out. So it's a good idea to wait until you know that you are ready to be out, and that you will have the support of family and friends.
2. Coming out is not a single step. Some people tell friends first, others tell siblings first, still others tell parents first. But for most people it happens by degrees. If you aren't ready to have the conversation with your parents, then by all means wait.
3. Coming out is a positive experience. You are full of anxiety and you are doubtless stressing out. But coming out is an affirmation of who you are. To my mind you don't "admit" to being gay, you share something important about yourself. That's not to say that it will be a jolly time--some friends or family might react badly, at least initially. But it is always better that they know than not.
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--James