I am a survivor of vocal nodes -- and I know exactly what caused it -- trying to sing as loud as the saxophones in a practice room preparing for a musical theater production. I actually felt something rip at the time. I regained my voice in a couple of days...but over time, scar tissue built up and I lost range, got very scratchy, and ultimately had to have surgery. I was not allowed to talk or whisper (which is even worse for your voice) for a month. It's been about 15 years now, and all is OK.

You really must see a specialist if your voice has really deteriorated; it can be a sign of a serious condition. But assuming not,

Here is a piece of advice from my ear/nose/throat doctor:

To protect your voice, use a higher speaking voice! He said too many women want to sound like Lauren Bacall (and no, my speaking voice is not THAT low). I didn't make a change in how I speak normally, but I do this when I need to protect my voice for a gig or start to feel it getting strained even in just a social situation.
Raising your speaking voice is especially helpful if you are in a loud environnent, such as a club where everyone is talking or there is music in the background. Pitching your voice higher lessons strain on your vocal chords. Try it, you'll find it really works.

Another way to be heard without talking louder and straining your voice is to throw your voice more through your nose; it may not sound as lovely, but you will be heard.