Sorry you are dealing with these troublesome thoughts right now.:( It can be just as distressing as the physical symptoms of anxiety/panic.
Have you used therapy worksheets in the past? I know it is hard to slow the mind down enough to even attempt this type of exercise...but give it a shot.
Taking the most prominent thoughts and breaking them down with these self-help pages can really help to break the intrusive thought cycle.
Here is the link for some good ones.:)
Therapy Work Sheets:
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Hoping you feel better soon!
"Courage is not the abscence of fear, it is feeling afraid and doing it anyway!"
"Worrying does not empty tomorrow of its troubles...it empties today of its strength."
Corrie Ten Boom
Panic Syndrome recovery due to CBT