@colleenyoung Maybe you will want to cross post this to other groups.
My husband has fought Squamous Cell Carcinoma since summer 2015. He has had many surgeries, many rounds of radiation, Erbitux from September 2016 to June 2017 when a pet scan showed that while the Erbitux had worked on the cutaneous lesions, the cancer had metastasized to his liver, diaphragm and neck.
He was started on Keytruda in June 2017 and PET scans in October 2017 and February 2018 were clear. He continued having profound fatigue and it was always blamed on "chemo" and radiation. Sometimes he would fall asleep in mid sentence. The Keytruda took his transplanted kidney – that is why we waited so long to try it. Of course, hindsight is 20/20. We now do home hemo-dialysis four times a week. When we do the dialysis, we have to keep a record of his blood pressure and pulse every 30 minutes.
Last Friday we had an appointment with his Nephrologist, who also acts as his primary doctor. One of the nurses from the dialysis center was there. I had the records from our prior month's dialysis sessions, so I gave them to her. She leafed through them and said, "Why is his blood pressure falling into the 40's?" She brought it to the doctor's attention. Turns out that a legacy blood pressure medicine called Atenolol was the reason. My husband had been taking it for years. He stopped that day, and the change has been nothing short of miraculous. Today he got out in the yard and worked for the first time in a couple of years.
The reason I telling this is that you should question everything. The pharmacist is so right about knowing WHY you are taking what you are taking. That nurse gave my husband a chance to live again, instead of just existing. QUESTION EVERYTHING!!!