Why does my singing voice sound different after having acute bronchitis?

On the 7th, I went to see the doctor and he diagnosed me with acute bronchitis. I had to take medication for ten days straight. I started singing lightly in choir cl on the 10th, and I have been singing only in cl since then. (I sing alto, so I didn't really have to hit the high notes.) However, when I sing, my voice sounds different from before I had acute bronchitis. I can't sing as loudly as before, my throat gets dry more easily, I get out of breath more easily, and I feel like I sound slightly nasally. What can I do to fully get my singing voice back?