Wow, big stuff for such a young person. There must be some reason it is so hard for you to talk to your parents. Is there anyone else in your family you trust? You need to find someone, quickly to talk to about this.
There is no easy way to tell someone you are pregnant if this is not welcome news. You just have to come out and tell him and deal with his reaction. Obviously you are not sure how he will react or this would be easy for you.
If he cares about you, that's what will be important to him. If he doesn't then it's best you find out now anyway.
Keep in mind this will be hard for your boyfriend, too. He will be scared and unsure about what is going to happen, too. He may even face charges of some sort if he is enough older than you (that varies state to state).
I'm concerned about you, having unprotected sex at such a young age. I hope you will get some counseling to help you get through all of this. Tell someone older in your family that you can trust, or at the very least a teacher or a school counselor so that you have an adult help you sort this out. Give your boyfriend a chance to step up and be straight with your family if he can. Then the two of you tell your parents if you don't think it will be a dangerous scene. Only you know what your family is like. But you obviously- can't keep it a secret forever.