Pre-birth depression?

I was due on the 18th of June and my baby still hasn't arrived. I don't know why but today I began to feel very down. I want my baby so badly, i feel energized and alive every time I think labor is about to start, but it's always false. I'm beginning to feel disappointed in the whole process, and these feelings are scaring me. Every little thing that happens gets me so psyched about welcoming my child & then when it's not it's almost sad to have to crawl into bed instead of hop into the car to the hospital. I know this is so strange because here I am, incredibly blessed to have this opportunity, & yet I'm feeling so down. My hours are off because I nap so often (I'm exhausted) & sometimes I find myself up at night and very lonely that I begin to talk to my sleeping husband. I just had my first bloody show about an hour ago, but nothing has happened since. I know these feelings are temporary, but I was wondering if any of you mommas find yourself having sad moments & disappointments in these last few days. It's like being over prepared & feeling like every day that your baby isn't here is a day stolen from you. I know I should be enjoying this time and I am...they're just weak moments & I'm a hormonal overly- pregnant mom. 
Thanks for listening