There should be nothing painful about the actual stem cell transplant.. it’s basically a transfusion. There may be some bone pain as the cells rapidly grow in the marrow. (I Had one). But, I’ve never heard anyone call the process painful.
Most pain crime from gvhd or chemo related issues .
I also am an administrator on a sct/BMT page (for 7 years) with about 15k members.
evidently there was host versus disease and the changing of the blood type was painful.