Can Principal deny me for something that has nothing to do with my preexisting condition?

I was diagnosed with breast cancer in 2011 and I had a double mastectomy in 2012. At that time I did not have STD coverage with Principal. However, I did purchase STD in January 2016. I made the sales representative very aware of my pre existing condition and I was told I would be covered as long as my breast cancer didn’t return and cause me to be out of work. On July 20th I was sent to the hospital by my family doctor because they thought I had a blood clot in my lungs. The angiogram was clear. So, extensive blood work was done. I was then referred back to my oncologist because my estrogen level is 4 times the normal limit. My oncologist has scheduled with my Gynocologist to have my left ovary removed. I’ve already had a hysterectomy. So the left ovary is all I have left. I am extremely fatigued, vomitting daily, and very achy. Principal has yet to approve or deny my claim. The representative on the phone said this could be stemming from my breast cancer. I am shocked! This has nothing to do with breast cancer. Yes, I am being seen by my oncologist but at this point I have no cancer diagnosis. Can they deny me for having an ovary removed because its related to breast cancer? I had no idea they would be so hard to work with or I would have never purchased the policy. I have done all the leg work, from faxing in all doctors records to prescription records and giving them the contact number for every doctor. I feel they are searching for a reason to deny me now. The representative originally said I had to provide Oct-Dec of medical records to show 90 days prior to the policy. Now they have decided to go back to Sept, 120 Days. This is just another stall or attempt to deny me. This can’t be legal. Thoughts?