Do you think i could join any branch of the military with myotonic dystrophy?

No, but thank you: for your interest to serve. That's a tough illness to live with, and you would be stressing your muscles out too much doing excercises even to pass Basic Training, regardless of MOS. If you want to serve, there are jobs in the civilian world with various branches of the government that would try to accommodate your illness if possible. The fed is very open to supporting employees w/ special needs.