Tell the truth to everyone involve. Visit your doctor regularly, graduate, get married and get a job.
Talk to the father of the baby, does he want to be involved in this child's life?. Can you take care of a baby, will your parents help? At 19 years old you need to consider all these aspects and weigh up whether your baby would be better off with adoptive parents.
I know it must have been a shock but you should think carefully about what would be best for the baby that should be the priority.