Overwhelmed

My husband and I have been married almost a year and just found out that we're expecting a baby. I'm almost 5 weeks. It was planned and we were blessed to have it happen the first try. I am a nanny and have always loved kids and wanted a bunch - it has been my ultimate dream to be a mama. 
But ever since I found out I was pregnant, I keep going through these emotional waves of not feeling "ready." It isn't constant, but when it happens I feel so overwhelmed to be pregnant and sometimes wish I wasn't. I don't feel competent to be a mom and am just feeling uneasy about it. I'm not sure if it's the hormones that are making me feeling weird or what. Anyone else experiencing this? Is this normal?