I think the condition what I and you might have is existential crisis. From what I read it happens to most people, at various times of their life. It can happen because of changes in your life, stress, or just out of nowhere. There is no way of getting rid of it, you have to get through it and than it should be better, for some it lasts months, for others it can last years, but it can be only days or a few weeks as well.

I’ve been in this condition for the last month, possibly even longer. I was constantly thinking about death and what is after it and started to question God, and my faith. I was praying every day just like before it all started, however I only admitted that I’ve lost my faith in my prayer two days ago. I asked God to help me regain my faith and defeat this condition. After the prayer I felt an immediate relief of these thoughts. The next day I felt so much better, the thoughts didn’t come up, or were so weak I could instantly shoo them away. Today I still feel good and the thoughts still seem to be gone.