Baby's

My boyfriend of 2 years want's a baby, but I'm not ready to get pregnant. So far we have been careful, and using protection. He has poped the question twice, "would I have his baby"?. I'm not really sure if I'm pushing him away by saying not right now. I'm affraid he might find a girl that will say yes to him, and leave, I love him a lot, but I would like to finish school first.