If it's something that is going to kill you, even slowly, I would let it....you must have some quality of life still? You can eat and drink pleasurable things and watch TV and read to distract? Mentally, you are still well? You can sleep? Your nervous system is normal? You have comfortable accommodations? Sometimes you are well enough to even do some normal things? I'm not trying to discount your situation... only you can decide. But if those things were a yes for me, I wouldn't do it.
If I had "normal" pain, or a disease that would kill me, I would let it. I actually beg for something terminal. I never would have considered suicide if I were not iatrogenic harmed, plus don't even have the comfort or pleasure of food because of my stomach. My relationships are in the toilet because I can't be well with my pain and suffering as everyone wants and needs me to. I can't cope with this. There's no quality of life for me at all, only unnatural torture. What's holding me back right now is I don't want to hurt the ones I love, the fear of after for me because of my faith but most of all, because I have only a violent method available.
If you have the above as I stated, one thing is to try and focus on those things and have immense gratitude for them. Keep a gratitude journal, connect with the ones you love. Have you tried therapy?