What’s going on with me?

I’m almost 30 weeks. Getting down to the wire now, and up until a week ago I was excited and happy to be pregnant. But it’s now getting difficult and I just don’t feel the same way. I have anxiety over the way my life is going to change and I don’t feel happy about it anymore. I’m not neglecting my health or anything. But mentally and physically it feels like I’m getting sucked dry from this baby. Like the little maternal instinct I had is gone and I’m worried I won’t love him when he gets here. I feel ashamed for feeling this way. I’m scared. Is this depression?