I am so sorry.
Yes, I have most definitely been plagued with thoughts of doom, illness, death. Not only myself, but my pets and other loved ones. Obsessive, relentless thoughts.
I have bipolar disorder, so I'm on plenty of meds. The antipsychotic I'm on does help a bit with the thoughts. I'm working with my therapist on "being in the moment." I will say that while it takes commitment and very hard work, I am experiencing a measure of relief. The relief is tenuous, though...it feels like it could topple if pushed too hard. But, I don't know what else to do except keep trying.
Intrusive thoughts are so very difficult to alleviate. And what are they but anxiety...I try to keep my focus on treating the anxiety, rather than treating the thoughts themselves. Somehow that can be helpful.