This is my first post here, so I apologize in advance if I don't properly follow the conventions.
I've looked through the old tags here and executed my best Google-fu trying to make an educated decision, but since I'm trying to backwards match an illness to its symptoms/treatment side effects, it's difficult to know how to search.
I was initially planning on using a cancer diagnosis, but again, I am having a hard time finding one that meets the scope of my requirements and, short of researching them *all*, I am really not sure where to start looking.
Here is what I need:
Modern day setting, Britain. My main character is a male in his mid to late-twenties. He has a terminal illness, which he has had for a while and is either beyond treatment or not responding to it. He is going to die in the not too distant future. For now, he is still largely functional - able to walk with a cane etc, but he tires easily and must frequently turn to hard core pain medication. He is a pianist and I would prefer that he still be able to play *some*, even if only occasionally. Would also prefer that it not affect his mind outside of the drug interactions.
Here is the embarrassing part - I need him to still be *technically* capable of having sex and producing a child. I know that both chemo and radiation treatments affect a man's fertility to a significant degree and that fertility *can* come back down the line, but I presume this would be at the end of successful cancer treatment, not after a no-holds-barred, do whatever we have to do sort of attack on the illness.
I have googled the heck out of cancer treatments and fertility issues and I see a lot of 'can affect...', but it's all very vague. I walked back through quite a lot of the illnesses to order, but nothing popped out at me.
Oh, and to clarify, this needs to be an 'oops' situation. Unprotected sex = pregnancy despite illness/treatment rather than intentional preservation of fertility through sperm storage or similar.
So what I am looking for is a cancer or terminal illness that fits the above requirements.