If you want this baby, then don't let anyone's opinion change your mind. Its YOUR body and YOUR baby. Not theirs. If they never come around, then they are missing out. There's really only two ways to go about it if they're really upsetting you:
1) You sit down with them and have a chat about why they're so upset about it. They might be worried you're too young or they're going to be stuck raising the baby. They might just be shocked. They might dislike the father of the baby. Once you know the problem, you can work on a solution. If they think you're too young - prove that you're responsible enough to raise a baby without relying on them. If they don't like the dad - show them what you like about him. Obviously without knowing your situation I can't offer specific advise, but they're the big reasons parents are upset when their daughter gets pregnant. Letting them know that their actions are really upsetting you is important too.
Option 2 is you let them come around on their own. Its possible shock is their main problem and once they've calmed down they'll want to start talking again. I probably wouldn't recommend this one as it really is just running away from a problem, but if they're the sort of people who will not sit down like mature adults, you might need to just let them be for now. Obviously if you live with them, then this isn't really an option at all!
Good luck, you can always talk to the people on here if you're feeling alone x