Hi MarkofKane -
Well, I can only tell you from my own personal experience - a real doc would have to diagnose your specific conditions. But I definitely have obsessive thoughts and it is separate from my panic disorder. Not that they are not unrelated by any means! But I can have the panic and anxiety under control while still having the obsessive ruminations.
It's OCD for me (obsessive compulsive disorder). I will have uncontrollable thoughts that run circles in my head about everything from minor issues like a school affair to death and terminal illness! I personally have found that an SSRI helps me stop those obsessive thoughts - but I'm also currently working on new techniques like thought stop/thought replace, distraction, etc.
I would suggest seeing a doctor to help you determine the root of the thoughts - it's like what came first, the chicken or the egg? :) Is your anxiety causing the thoughts or are the thoughts causing your anxiety?
The obsessive thoughts are the worst - I can't stand them - so I do feel for you and you are not alone!