It's often referred to a perinatal or prenatal depression. I do second what the other user said and think counseling would be really helpful as it can continue postpartum and increases changes for major depressive episodes. A lot of it could be normal and just a phase of pregnancy, but talking to someone who is neutral and can offer you some insight is pretty helpful!
I had this problem with my first born please seek counseling even if you can't pin point why you feel this way as it can and most likely will continue once baby arrives it did with me and its normal to have emotional imbalances during pregnancy due to hormones and body changes hope your feeling better soon x
It wouldn't be postpartum depression because post means after but you can definitely just be depressed. A lot of anxiety and hormones are being released
Must be because I'm feeling the same way. I'm 10 days away from my due date and feeling depressed.