I'm a CALS and I think about this (almost) every day. It INFURIATES me that, not only is assisted suicide unavailable in 48 of 50 states, it isn't even spoken about. I think that when my PALS goes, I might get active in the cause. I know that if it were me, I would want to go drugged to the gills, high, happy, and sleepy. And I find it frankly absurd that you can put a pet down to save them pain, but you can't do the same for loved ones that ask for it in the first place.
Having said that, we were at the same place a few years ago, and my PALS is still going strong. Most days I can get a smile out of him and on our best days, I can make him laugh. He lost 95% of his muscle mass within 2-3 years, a devastating blow to a former skateboarder/circuit board engineer. . . but I don't think either of us would sacrifice a day of that for a premature RIP.
Life is different, for both us. Hard, obviously. Sisyphean, of course. But, you know, you adjust to the challenges.
Don't give up just yet. You might have many good, albeit difficult, years ahead of you.
If not. . . I've heard of other legal options, which I won't mention here. But please, please, give yourself a chance. It doesn't have to be a death sentence and it's far, far too early to succumb to this [many expletives deleted].