Depression in 2nd trimester?

Im 21w 3d and the last couple weeks Ive been feeling so crummy. I wake up feeling so miserable like nothing could cheer me up in the whole world. I just want to stay in bed all day. 
I feel deep down excited about this baby but mostly just scared. I don't know how to be a parent! I don't know how to buy the best car seat and breast pump and vibrating swing seat thing... I wanted a baby for so long and now I'm just mostly freaked out. I mostly don't feel all the happy glowy pregnancy things.. I feel fat and hungry and depressed and anxious and tired. Is this normal?!?