I can relate to your obsessive thoughts. This has happened to me also. Just know that thoughts are things that just past by your mind. They only have value if we give them energy. Do your best to devalue thoughts that cause unhappiness. Just let they go by like a cloudy in the sky.
Yes, our bodies live and die... don't believe you have the answer to the next chapter after the body passes. We human know a lot, but we also don't know much about the spiritual world. Only the ego can see a sad ending, the spirit alway sees peace and love.
Pray... you can see thing differently, do not over value your thoughts. Notice this moment... I'm breathing, I'm sitting in front of my computer. Things are calm. All the noise is coming from a restless mind. The mind is not real its a day dreamer. Wake up and be. Take a walk and feel God's presents walking with you. God is always with you even if you are lost in thoughts (like most humans are).