Where's the excitement?

Don't get me wrong, I feel absolutely blessed and lucky that I am pregnant and I am looking forward to my son having a little brother. But this pregnancy just feels different. I don't know if it's because I'm working (and I don't like my job and am always exhausted) or if it's the nervousness about trying to take care of a 2 year old and a newborn at the same time. Like, I know the first couple months are going to be sleepless and hard trying to figure out the balance. Did other moms feel this way with their second? I'm trying to be optimistic but I really don't feel that excitement that I did with my first :(