First of all CONGRATULATIONS!
Now, that is a decision you can only make by yourself. Don't listen to what other people say, you need to weigh the pros and cons; can you suport it financially as well as emotionally? Is the father still in the picture? There are a hundred different questions you need to ask yourself before you can make your decision. It's probably really hard. I say probably because for me there was no question. I am keeping my little girl no doubt about it! I got pregnant like 2 weeks after my 18th birthday and I am about to go into labour any time now. Becoming a mother at a young age is really, REALLY hard! Your life will never be the same again. Are you ready for that? Are you willing to give up the rest of your teen years? Are you ready to devote your life completely to your child instead of going out with friends and having fun? It is tough, I still get sad sometimes b/c all of my friends are having tons of fun while I am having tons of pain! Only a few of them rarely even call me anymore! But it's all worth it for my babygirl!
So anyway like I said, you have alot of thinking to do! But good luck on whatever decision you choose, and just to let you know I'm here if you want to talk!