Well, if you "kinda planned this," then you might want to look into resources about how to carry to term and get help with the baby afterwards. Because it sounds like this is a wanted pregnancy, even if you are sacred about what will happen. There are reasources to help you graduate and get going with life, even when pregnant or when caring for a kid. It is not necessarily easy, bet then neither is parenthood when everything is well and ready either. So look into resources. Ask your school counselor, get help from your parents. Which brings us to....
As for telling your parents, there is no easy way. Ask yourself if they are supportive. Yes, parents get upset about all sorts of things, but when it is *really* serious, then you probably have a good idea what they will do. Will they help or would they kick you out for not living up to their expectations. If they are not the type who would kick you out for being "bad," then they likely will support you. Because you are their daughter, and parents generally don't like to see their kids fail. And you will likely need their support if you decide to go on with the pregnancy and raise the child.
Now, if you feel thoroughly trapped and with no friends, family or support, then it would indeed be so tough that it would be almost impossible. Not completely but almost. If you have big plans of graduate school and science careers or such, then this likely could stop you. If you decide on an abortion, be sure that you can accept such a choice and talk with the counselors at your local clinic.
But remember that it is your decision. Pick the decision that will work the best for you, and then go looking for how to make that happen. Sorry that you have to grow up a bit fast here and deal with this at your age, but you can get through it.
