I understand what you are going through. I have had panic attacks due to thoughts such as what you describe for years. I found that taking up meditation helped me or just discussing it with my parents have helped me calm down and be able to go back to sleep. I hope they go away for you and you can get some quality sleep.
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It is a very distinct tribute to be chosen as the friend and confidant of a cat. ~ H.P. Lovecraft
Why so serious? ~ The Joker
You can never get a cup of tea large enough or a book long enough to suit me. ~ C.S. Lewis