Hi I'm new here too...
I remember what it felt like when I was first diagnosed... its such a confusing time, and while your working out your meds you can feel so out of control... there were many times where I was really worried where things would end up, and that I would give in and kill myself.
It's great to hear that you are thinking about spiritual things, I find it really encouraging to read the bible, that I could cry out to God when things are bad, and the support of my Christian friends and Pastor has been so amazing. I don't think that any of us "deserve to feel this way", but it is the reality of living in a fallen world, we are broken, no longer a perfect image of God.
As for why - we may never know in this life but God can use bad things for good (Romans 8:28)
When you are troubled call out to God "Cast you anxiety on him because he cares for you"

All the best, hang in there it does get better.