Oh man I could have totally written this post after the birth of my first daughter! Your feelings are so normal, this is baby blues to the tee. I was weepy and sad for weeks after she was born. I remember just crying when friends came over and asking them "When does this get fun???"
All to say, it is a horrible combination of hormones, fatigue, pressure to figure out things you've never done, and yes mourning your past life. But it gets WAY WAY better! In just a handful of weeks you are going to start feeling happy, confident going out and about, and your little one will start sleeping longer stretches. Do get outside and go for walks! Watch funny shows, find distractions!!! Right now you just have to ride the emotional roller coaster till the gloom passes, but I promise it gets better! I think it has to be quite prolonged before it is considered post partum depression, but do seek help if it persists. But most of what you're describing sounds like baby blues.