Ariellagrimm,
i know you are scared, I couldn't imagine being in your situation when I was 16. But you have to tell your parents (sorry to sound like a broken recorded here, but there is a reason why we are all telling you this, specially since you have no one else to help.) I am sure if you tell them, they will not tell the rest of your town, they will help you. I know people that where really scared to tell their parents, and yes the parents where mad at first, but then they came to realize the fact, their daughter is pregnant and there is nothing that can be done now. Your parents love you, and all they want is to make sure you are okay. You might have been able to hide the fact that you are pregnant up to now, but you can't hide it when you are 8-9 months, and no matter how well you think you are hiding, people will talk. And it would just make things worse if your parents found out from someone else, or on the day of your delivery.
It will be hard to tell your parents, but it will be even harder to try to do this by yourself. You can't think of the consequences of telling your parents, you have to think of the consequences of not getting the proper help and care for you and your baby. Whether your parents are rich , poor, famous, the king or working at mcdonald's, every 16 year old that got pregnant is going through the same thing you are, you are not the only one, but in every situation you have to tell them. Even 30 years old women need help via the doctor and/or someone else. You will need the help, specially since you are so young. You will need someone to drive you to the hospital, or to get you help when you start labour. Even if you are giving the baby up for adoption, you will still need the help up to that point (even after with the emotional part).
Have you talked to the adoption agency ? They might be able to help as well.
I don't think anyone here is trying to lecture you or anything, we just want the best for you and your baby.