If he wasn't prepared to be a father, he shouldn't have helped to create a baby. He should have thought about that before. If you want this baby, that's all that matters. He has two choices: either get over the fact that he got you pregnant and step up to the plate, or resign himself to the reality of paying child support when the little one is born.
The funny thing about some people (men and women both)... They don't consider the consequences of their actions until the consequences happen... And then they want an easy way out of it because they "weren't ready". It's a hard lesson to learn for some people, but that's life for you. Congratulations on your pregnancy, sweetie, and don't stress about convincing your man. He'll either come around on his own, or he won't. Either way, he has a responsibility to you and your unborn child.
*edited for spelling*