Ok, here is what you should do:
First, Stop being scared. It's not going to help you and it can cause you to have actual physical pains that you wouldn't have otherwise.
Second, Tell your parents NOW: 10 weeks is a good time to start seeing a doctor, especially if you are only 13. I am guessing that you haven't done that yet since you haven't told your parents. They need to know at some point....because they are going to realize you are because of your health or because you will begin to show. They are the ones that are going to have to help you with the pregnancy and your sincerity and truthfulness at this point is critical. If you feel that you cannot tell them to their faces, write it out on paper....tell them your fears and your misgivings and how much you need their help more than anything else at this time.
I know you want to keep the baby, but you can think about it for a while. Pregnancy lasts nine months and after you have talked to your parents, and considered all the possibilities, you might decide that adoption is the best thing for you since you are not considering abortion, which, once done, can bother you for the rest of your life.
I am very glad that you are mature enough to accept the consequence of a baby as a result of having sex, but at 13 you cannot provide all that a child needs, unless your parents want to take care of the baby almost full time. You still have a lot of schooling head of you and you will also need to get a job to support the baby.
Thirdly, Try keep as healthy a lifestyle as you can........This pregnancy is going to be hard on your body. You will be fine in the end, but you will be exhausted and need a lot of time to catch up from the strain, just as every girl would, but your body is busy growing too. It isn't much easier after the baby is born....you won't sleep much and most of your time will be spend feeding the baby, changing diapers, and holding him.
The rest is up to your parents and your doctor, and best of luck.