I was diagnosed at 23, and I totally agree with how rough it is. You can't control a lot of those external factors, but one thing you can do for sure is insist on self-care. Make sure your GMs know that you may have to take a break to walk or stretch or take meds, so your character should be easily "put in the backpack" for a few scenes. Let other folks help you with things that can't be avoided, like getting food, and insist on disability services for the stuff that can--you DO deserve to walk up to the "VIP" window and ask for a registration process that doesn't wreck you physically.
I've been working on this for 16 years now, so if I can give you support or any other insights for work-arounds, just let me know. And keep doing what you love--it makes the pain worth it, sometimes.