You need to work on this at your own pace, one that you can deal with. Don't try to push it and overload yourself.
The when and where and how much of your story you share is entirely up to you. As time goes on you can add more of the information as you feel safe. The only one that needs to believe you for the healing to start is yourself.
Write a bit of your story down on a piece of paper. Start with something simple like, "I was abused" and read it outloud to yourself. When you are ready do it again another piece of information, "I was abused by my step-father". Keep doing this, adding the bits of information as you feel comfortable/safe and as they come to you. Remember to be honest with yourself, this is about healing your wounds, not protecting those you think will look bad. And be open to the feelings you have and to the bits of help that come along.
The same will work with telling your story to someone else. You don't need to tell them everything all at once. That small bit of the secret you carry inside of you says a lot, like "I was abused". I begins to let it out. And you can judge how they will react to the information you gave them, can they handle it, will they believe you, will they be supportive.
When you are ready, there will be someone to share it with. A family member, a friend, a therapist, a doctor, the guys here at MS, or that person you feel that you can begin to really trust.
Take care of yourself deej, and don't be afraid to post a question or concern or a feeling or a rant. We understand and we'll listen.
Pain is Temporary; Quitting lasts Forever. - Lance Armstrong