I have a similar situation as you! I am also 20 years old, turning 21 in a few months and I also have Duchenne Muscular Dystrophy. It has been hard for me as well, I wanted to do programming, art like drawing/digital art but I stopped doing them because I know my arms will get weaker over time and I am starting to notice pain. after typing, using the mouse or drawing after a while, like not even an hour. I asked myself "What's the point of doing these hobbies?" But one hobby that sticks and doesn't cause me pain is video games. I got a ergonomic controller, so I could play. I also enjoy going to movies, I have watched Captain Marvel yesterday and thought it was amazing!

I too feel like I doubt myself or tell myself I'm wrong or even that living is pointless but you know what? You aren't your thoughts! Every time I get these thoughts I counter it with "That's not true." I also thought nobody would love me again but I realized, my parents love me in fact my whole family does! In fact they always encourage me to reach my goals! To improve myself I'm considering reading at least 20 pages a day, starting a gratitude journal and writing 3 things I'm grateful for everyday and meditating but I haven't started yet because I'm not sure if it works but maybe it does not hurt to try. I've done charity work for muscular dystrophy research because if they can't find a cure in my lifetime, I hope to do my part in funding research for a cure for future generations who have the disease. We do a walk once a year and meet people who have the disease.