Nearly every state has a provision for minors to be emancipated and make their own decisions. You can look up your state and the process of emancipation on the Internet. Use Google to search your state's name and emancipation or emancipation pregnant minor.Some states automatically emancipate pregnant minors. Even if she is not automatically emancipated, you and she will be responsible legally for all of the decisions about the baby, not your parents. Many parents don't realize their children are allowed that responsibility if they become pregnant.
Although in some states, having intercourse at your age (specifically yours) with a minor is illegal. Other states allow it depending on the age of the younger person or the difference in the ages.
You would have to go through whatever legal procedure your state has established to gain emancipation in order for her to live with you. You need to consider the "bigger picture" which is that young parents have it much harder than older ones, and their children don't tend to do as well in school. On the other hand, if you can get along with both sets of parents, having parental support and loving grandparents for the baby can help things go more smoothly.