It takes nine months to have a baby which is about 39 weeks. This period is referred to as the gestation period and it is also the period that the fetus inside the womb takes to develop into a full grown baby.
Congratulations, I hope. You really need to read up on pregnancy and infant care, prepare yourself for what's coming. Two excellent books are: "What To Expect When Your Expecting" and "What To Expect the First Year", both by Heidi Murkoff. These books will answer most if not all your questions.
A great book you should get is called what to expect when expecting it will answer just about every question and a book about baby what to expect the first year. You should really tell your parents. They may be mad at first but you can't change what is done and your gonna need a lot of support!
You need to tell your parents honey! At least your mom, then she can break it to your father. She will probably yell at you, but it will be more out of disappointment than anger. Make it clear whether you want to keep it or not, and that it is your decision, not theirs. I know it's a scary thing to do but you have to do it. Your mom will be your closest friend during this time, so get it all out there in the open now so she can get used to the idea by the time the baby is born, ok? good luck to you... I know this must be very difficult for you and causing you a lot of angst :(