What is said here,
First of all:
Now to your problem.
Do not scream, shout out loud instead. Screaming (= shrill high tones) overuses the larynx which will result in the loss of your voice. Shouting (deep and loud tones) uses the stomach and is much more efficient. I know it's hard to explain but it's a matter of training. Your voice is a muscle. The better it is trained the more powerful it becomes. Singing trains the voice and the way you breath. A speech therapist could teach you how to do it right.
I suffer from pharyngolaryngitis during December and May (depending on the weather conditions at my place). It affects my nose and my voice at the same time. When your voice is gone do not whisper; whispering overuses your voice and will slow down the recovery. Drink much (warm drinks are recommended, even warm water will do as will soups, mainly chicken soup), have some rest and get enough sleep.
What Revell-Fan just said, you must use your stomach to force the air out.
One quick way to see what we're saying is sit down, then grunt. Notice how your stomach does the work? Now using the same method, say Who out loud using the stomach like you're trying to grunt.
Now practice with words you'll be using, like maggot, dogface, you're lower than the worm-crap that feeds on whale crap, etc...
Comes natural after awhile. Was a Fireteam/Squad leader in the Infantry many years ago. Once you learn how to do it, you'll never forget!