PPD.. Any second time moms get postpartum depression?

I feel extremely similar to how I felt after my first son was born.. but my brother (who raised me, was my best friend and absolutely the closest person that ever has or ever will be to me) killed himself the day before my son was born. I had to move across country ten days after my son was born, the day after my brother's funeral, leaving the father of my child and my home to a state where I knew no one. And inevitably became a single mother. So how I felt was normal for the circumstance.. but I feel exactly the same after my second son.. and I'm worried because I don't "have a reason" to feel this way.. why do I feel this way?