some general non-math-related advice:
a) get a full night's sleep before the test. studying is great....last-minute-studying...not so great. a well-rested mind is a fully functioning one.
b) drink a cup of coffee before the exam. some studies show caffeine increases alertness. don't over-do it, though.
c) on multiple-choice questions: trust your instincts. second guesses (when you're not sure if you're right) are often wrong.
d) when preparing, don't "go it alone". work with someone else. sharing your studies with someone else will both 1) lower your anxiety, and 2) give you someone to "bounce things off of" when you're stuck.
since you're a military person, look at the test objectively, like a military operation. yes, you will take some casualties. you probably won't get "every question right." the idea is to *pass* the test, so hit the targets you can, with a minimum of fuss. go through the questions once, answer all the ones you can easily, then go back for another "sweep". you're used to discipline, you can do this. stay calm, stay focused on the task at hand. they're just math questions, they can't actually kill you.
if at all possible, find someone "good" at math to tutor you. i don't know you, and i don't know wherein your difficulty lies. perhaps you hated your 8th-grade algebra teacher, and tuned everything he said out. perhaps you never *had* any good teachers, or even worse, had bad ones who taught you things in an incomprehensible manner. perhaps logic isn't your strong suit, or your memory is poor, i really don't know. but someone who DOES know you can see where your stumbling blocks lie, and zero in on them. you don't need to re-learn the easy stuff, over and over...you need to make progress.
one thing which may help (can't say for sure), is to bring some ear-plugs (if those are allowed). this might help you "tune out distractions" so you can focus on your work.
none of these things are "sure-fire remedies". tests exist to assess what you know, and if you don't actually know the material, all the calm and collectedness in the world won't help much. but at least doing something to alleviate your anxiety will let you "do what you can". best of luck to you.