Your wife has been near death's door and back. You will have carried years of worry over her life and wellbeing and it sounds like you are tired. For that reason alone (and there are many more reasons besides) I would strongly recommend you seek professional counselling.
However, no one can fully understand the inner journey our wife has travelled, and still is travelling to some degree no doubt.
When someone had a transplant they take awful medication to help prevent the body from rejecting the donor organ, the sort of medication that has terrible side effects. The sort of side effects that can keep you down physically. And that's without physically trying to repair all the toil of surgery, illness and massive weight loss.
I have no doubt your wife could reasonably be clinically depressed, it would be impossible for her to escape it fully with all she has been through. And it is common knowledge that depression is a libido killer. So is tiredness. And so it how you feel about yourself.
I have Multiple Sclerosis and fatigue is my nemeses. I feel as though my body is a shell that I am now imprisoned within, and my body has gone from being something I can enjoy and rely upon, to something that does not cooperate with me anymore and has become the enemy!
When I am so desperately exhausted my world narrows down to just trying to survive one moment to the next. I lost my job because of my illness, despite trying all I can to keep working, and I live with that loss daily. I can fully understand why your wife would fight to keep her job. It is her purpose, her identity, her distraction and probably the only thing that had remained a constant and therefore something of a comfort to her as she grapples to find her way back to some resemblance of her former self.
I am deeply troubled by the impact this has on my husband and on my two sons. You can be sure that even if she doesn't verbalise it, your wife will be acutely aware of how you feel.
You do sound like your priorities are a bit mixed up. Sex above a lifetime with someone you love? What would you do if years down the line you suffer with erectile dysfunction as many men do in middle age. Would you be mortified if you were left on the basis of failure to 'perform'?
Someone who has been/is still as ill as your wife will not feel the same about their body. It will be very hard for her to feel attractive anymore even if she has got the energy.
I hope your relationship is deeper that just the sex though. If you love her as you should, there will be times of self sacrifice needed, just as she will also need to self sacrifice if she hasn't already. Your wife will be grieving loses already, the loss of her life as she knew it, the loss of her relationship with you as she knew it, the loss of a body that cooperates. Don't make someone you love also grieve the loss of a son and a husband.
Someone pointed out that her illness is hereditary and asked you about your son and how you would handle him getting it too. It goes without saying that in sure we all hope that doesn't happen to you, but it is bound to cross his mind as he watches your reaction to his Mum.
Your comment about other people being interested in you is possibly a factor in your discontent too. Be very careful with that. There is a reason why we have a saying about the grass being greener on the other side. Don't be fooled, any new relationship will also have its problems, and could include illness too.
All of that said, I was brought up with a religious background of living according to the bible, and I do remember that it was often quoted how men and women should give of themselves to each other, both in practical love and in sexual love. Obviously this doesn't include reasonable problems like serious illness, but I would do feel a responsibility to find a way to fulfil that role as much as I can, and it does sound like you're upset because your wife is showing less interest in doing that than in working. Cue more counselling, I would suggest! Although as I said upstream, I can duly understand how she would be drawn to trying to get a sense of herself back through work when she probably hated her body at the moment and feels the least attractive she ever has.
Be glad you are not in her shoes, I hope one day you aren't (we all think "nothing like that will ever happen to ME") and that someone isn't on the internet talking about leaving you because of it.
When i worked night shifts I would look out of the window and notice how peculiar it is that the night really does get darker and darker and then suddenly reverses, just like the saying! Sometimes it's the darkest hour before the dawn in relationships too, and I have a sneaky feeling that if you remain true to your relationship now, and seek the help you clearly need, you will be glad for it in the future.