I think your parents will want to know that you have a plan. Contacting Birthright or your local crisis pregnancy center is a good idea. They have free counseling that can help you create a plan for parenting your child. When you meet with your parents, you will have a plan to share. If you attend a church, talk to your pastor. If you don't have a church, this might be a good time to find one. It's helpful to have the support of a community when you are pregnant. They can also be great guides for you and your boyfriend.
When you tell your parents, acknowledge that you have let them down. They will be disappointed. They know how hard it is to be a parent and they may have hoped that you would have waited. They may also be disappointed that you have been sexually active, hoping that this would have been saved for marriage. They will blame your boyfriend, although clearly it took two to create this child. Acknowledge all of these issues. Let your parents know that you realize they love you. Remember that their reaction, as difficult or hurtful as it may be, is probably based on their love and hope for you.
One last thing. Having a child is an incredible experience, truly a blessing. Your life will change in the most wonderful ways. No it won't be easy, but it will be worth it. Congratulations on this new life growing inside of you.