Depressed during pregnancy?

Anyone feel they're not excited for the baby to be? This is my second child, so that may have a lot to do with it (having less time for #1 and the relationships changing, etc.), but I'm just NOT excited. My mom keeps telling me that once the baby is here I will love him, but I'm almost feeling guilty about not being very invested. I haven't really given baby names a thought, and have done little to no planning for sleeping arrangements, storage, my birth plan, etc. Ahh! Motherhood has made me very lonely and isolated. I love my firstborn with all my heart, but sometimes I feel I need more.  My emotions are crazy!! Crying here and there and whenever I get a chance... Anybody else feel like this or know what helps get you through the day?