Is this a sign of post partum depression?

I had my son a week ago and I love him so much. But I just have a weird feeling. I feel like I should be attached to him more than I am. It feels weird to be a mom and I feel like he's not my baby. I know this sounds horrible I just feel like I should be so much happier. I was more overwhelmed with happiness when I was pregnant with him than I am now. I also hardly eat anything because I have no appetite at all. I feel horrible for feeling this way but I'm so confused why I feel like this. Could it have something to to with hormones?