I don't think this will help you, my voice changed years ago, my sister and I both. We were told it was because of the celiac disease though. One summer, we both went hoarse, for the entire summer, our kids loved it! At times, we had no voice at all. The doctor told me to never whisper, he said that is even harder on the vocal chords, says it makes them vibrate even more so. After that summer was over, we both have deeper voices, which we are told are sexy

, and we lose our voices very easily. This was when our kids were in Little League and all of our boys are over 24 now--I would say it had to be over 15 yrs ago.
Yours may be due to the meds, ours was more than likely due to vitamin and mineral deficiencies because of undiagnosed celiac, which still didn't get diagnosed for another 7 yrs or so after that. So many things can effect our bodies. I do believe that weezing from asthma definitely could cause voice weakness, it must effect the vocal chords.