I’m 22 and was diagnosed at 18 with scleroderma. What you described has been exactly how I felt over the past 2 years. I am currently classified under MCTD as I’m exhibiting multiple symptoms of all AI. The way I cope is I try and stay as active as possible and as hard as it sounds I try and think about something else.. My last hospitalization due to severe dehydration and malnutrition almost landed me a feeding tube but thankfully they tried nitroglycerin which helped a bit. It’s not an easy road. Lean on friends and family if you can I know it’s hard for them to understand but I explain to them it’s like having a constant flu. Also there is a MCTD support group but I also when I was first being diagnosed found support in the scleroderma one..
Good luck and prayers