This is a delicate topic. In my opinion, you shouldn't hide this from your parents. I am assuming that you are a teen and that talking to your parents isn't on the top of your list of fun things to do....but they can guide you with some good advice. There are many options that are available that they can help you with. Just remember, that your parents love you. Let them know what YOUR moral convictions are.
Your parents may be disappointed, and will be worried about you, but now is when you need them for guidance more than ever before, in my opinion. Find a good quiet time when everyone is relaxed, maybe after a meal and before any alcohol consumption. Ask to talk to them alone about a "serious situation" you are in. Once everyone is seated and listening to each other, talk to them openly, say something like, "Mom and Dad, I don't know how to tell you this, so I am going to just say it. I am in trouble and need your help. I am pregnant."
Be prepared for their initial emotional response, let them have their feelings and give them some time to try to catch their composure and shift back into less emotional thinking before you say anything else. When they realize you are asking for their help, and they are past the initial shock they may feel, you might be surprised at how lovingly they may respond.
This is not something for you to face on your own. It is not a good idea to try to hide it, in my opinion. Everything is different now that you are pregnant. Your life, your relationships, and your body are changing. You and your parents need to think of your health, and what steps you need to take now, and what decisions need to be made. Even if you already know what you want to do, be open to listen to advice from your parents before making final decisions.
If you decide to have the baby, then the health of your fetus now has to come first, too. If you try to hide the pregnancy, you will not be getting the proper health care for yourself, or the fetus, which is very important in the earliest stages of pregnancy. If you keep this a secret, your emotional state will not be at the best place for your health either. Consider that your family needs to know what your body is dealing with, if nothing else, in case of an emergency, so they know the right actions to take if something unexpected happens.
It will not be easy, but I think it will be much harder if you try to hide it.