Unexpected yet expected

I've been with my partner for 2 years. We moved in together last summer and got engaged in January. I just found out that I am pregnant yesterday. We wanted to wait until we were ready and plan it out as best we could but we were having the occasional unprotected sex, so I kind of knew it was only a matter of time. He's happy but mad at himself (as am I) but he's still in disbelief. This isn't my first pregnancy so I can get through this but I'm worried about him, this is his first. Any advice on how to help him without scaring him?