I want to just back up something already said because it's a pretty big deal:
He’s already talking about buying a new house and getting a mortgage and getting money together and it all seems so real now. I’m so happy that he wants it I’m just worried I could be rushing but I would love a baby and I just don’t know what to do.
This certainly sounds like a pressure-filled push to me. Especially given your age, his, and the fact that a year isn't very long to be with someone to be planning something as big and the-rest-of-your-life as creating pregnancy and parenting.
If and when we really want to only move forward with something with someone else if and when they, too, want that thing, we don't start talking about all the steps we're going to be taking. That's pressure. That can even become coercion. That is NOT the way to make a family with someone where it's a given everyone involved wants to freely do that. I can see why you're feeling how you are, why you seem to be feeling pressure: I think that's because he's exerting it.
This is your
life. In the event you letting him know that you are not ready for this, and that you have other goals you are working on and want to complete first -- let alone that 18 is awfully young to become pregnant, go through a pregnancy, and start parenting -- hurts his feelings, his life will likely not be very impacted. At most, he might have an extended moment -- an evening, maybe even a few days -- of just being bummed. If he's not such a great dude and this is about control, he might be more hurt than that and even angry, but trying to avoid that isn't the way to go because if he's the kind of person who wants to control you and push you into family, that's something you want to find out so you can get gone before things get even worse, you know?
But again, this is your life (especially since culturally and legally, mothers do bear greater burdens and greater responsibilities; his freedoms won't be impacted in at all the same ways, or to the same degree, yours would be). His hurt feelings vs. your potentially derailing your own goals and dreams, or starting on a part of life earlier than you want or are ready for just can't complete. Your whole life should win, hands down, and I'd encourage you to stand up for it. If he's someone who does love you, and for who you are and want to be, not just what he wants, he'll encourage that, too, even if it means he doesn't get what he wants for himself from you as soon as he wants it.