Can MOO deny my claim on the basis of preexisting condition when my condition is not preexisting?

I’m a heath care professional who treated severe trauma patients for 20 years. I developed PTSD and now I can’t even see trauma without having a major panic attack, even on meds. I had never had a single panic attack prior to getting PTSD. I’m published in the world’s most prestigious journals and text’s for my accomplishments. Mutual of Omaha is denying my second claim because I took Clonazapam for 13 years prior to developing full-blown PTSD. Now on many new meds and I let my license expire because I will never let myself be destroyed like this again in my profession. They said it is all preexisting because of anxiety. My doctors are all saying PTSD is, in no way, the same as general anxiety. However, Mutual of Omaha is saying my condition is preexisting. If it was, then how come I could perform my job and considered one of the best in the world by some trauma surgeons I worked with, but now I can barely drive across town? Can they get away with denying me for a condition that I’m not even limited because of. PTSD and anxiety are different conditions entirely. I’m 100% thinking of sewing as my doctor’s say I never had PTSD. Now I do and can’t work. Mutual of Omaha is denying my claim. My doctors insist my condition is new. Now what?