I agree that you should talk to your T about what you're feeling.

I learned that my marriage counselor's wife has a serious illness (don't know which one) that causes her to need home health workers there with her when MC or their kids (teens) are not. I felt unsure if it was OK to ask him about it, but he said it was OK, and it helped to talk about it for a bit. He said it was "manageable" and there were much worse things they could be dealing with. He asked if I felt like because he helped me emotionally, did I feel like I needed to do the same for him (or maybe he would take away his care)? I said it wasn't so much that I felt like I *had* to, but that I *wanted* to help him, too because I cared about him and felt compassion for him. I also brought up something like what you said, where I felt like my problems must seem so minor if he's dealing with that. I forget what exactly he said, but it made me feel better. I know he loves his job, so it's probably a sort of escape for him. I also worried that he'd have to leave his job because of it (he's had to take some days off), but he said, "I still have to pay the bills!"

Also be prepared that your T may not want to discuss any details of her illness, but she should at least be willing to talk about what it could mean for you and whether it would affect her ability to focus on you. (Obviously, she probably doesn't know what course it will take, but at least what she knows now.)