Firstly - congrats!!
I was in the same situation only I was 16, my then DP voiced his concern (obviously we were both very young), I was doing it with or without him, no matter how young I was, an abortion was out of the question! He's a very doting dad now (although we never made it - and had a 2nd lol).
He will come around, maybe not in a relationship with you, but he'll definitely play a role in DD/DS life, he's just super scared!