My bf was the same way until he could feel the baby. Then at our 2nd ultrasound he cried and later told me he was in love with our baby. In the beginning he would change the subject if I brought up baby stuff. For some men it takes time. They don't instantly bond with the babies like we do.
He is jst scared..just give him some time and let ur belly get bigger and let it actually sink in and once he/she starts to move I'm sure he will b excited as u are :)) w my second we thought my daughter was goin to have many issues before I got far along in. My pregnancy and my husband was kind of distant w the pregnancy but once we found out everything was ok we started to bond with her and talk to her and wanted to feel her move and all tht wonderful stuff! I'm sure in time he will b excited:))
he's probably just worried it will happen again, i think with time (after the first trimester) he will probably get more excited. i would just give him time to let it sink in.