Scared..

I thought I wanted a baby. My husband and I decided not to try but also not to use protection of any kind. We said if the universe wanted it to happen then it would. It happened. I'm 15 weeks now and I was all nerves in the beginning and expected by now that I'd be excited. But I'm not. I'm scared and don't want my coworkers to know and I just want to pretend it's not happening. But part of me (especially when I'm home) is waiting for the day where my bellys big and I could feel the baby move. But it ends at that. Birth doesn't scare me but the actual human being I'm to care for does. I'm just so back and forth. Is this normal?