Alice, it might be a good idea to get checked out by the doctor just in case it's a physical cause, and one that you should be worried about. No doubt you've thought of this - and even the worry might be tightening your throat and making your voice tighter and coarser.

It's not a good idea to drink spirits; drink beer or wine, but spirits are hell on the vocals.

And for all ye asthmatics, if you want to use the ventolin less, try some buteyko breathing; it helps to lessen the need for inhalers. If you also use a becotide inhaler you'll get a sexy croak to your voice.