Prenatal depression

Has anyone been diagnosed with prenatal depression? What are the symptoms to look for? I can’t figure out if the way I’m feeling is normal for 30 weeks (not suicidal or anything, but I don’t want to do anything with anyone. I haven’t wanted to for most of my pregnancy) or if they are symptoms of depression. And can you develop postpartum depression (I know “postpartum” really means after birth) before ever having your baby?