Here's the thing about medicine:
"When you hear hoofbeats, think horses... not zebras."
98% of the time it's something easy, simple, and "normal". ANY set of symptoms could be one of about 200 - 500 different things. BUT it's USUALLY one of say 5 things. If it's not those 5 things... they move on and test for the next 5. If it's not those 5 they move on and try the next 5. They just keep moving down the list. Fortunately you don't have to test for *everything*... because one test will usually eliminate 20-50 things. So the possibilites list gets shorter and shorter with each test.
It's a lot like parenting. If your baby is crying in the middle of the night you don't automatically assume that a stranger has broken into your house and pinched your child. You assume that they're hungry / wet / scared. If not one of those things then you try and figure out if they're sick... and if they're not sick if they are in pain (gas/ teething/ bruise/ ears/ etc). FAR down on the list would be a stranger breaking into your house to pinch your baby (but it does occasionally happen).
Medicine works the same way, but it's trickier because there are SO many more options. Doctors look at what is most likely first and then start moving down the list in the order that makes the most amount of sense.
By trickier, here's and example: My husband wasted 4 months and several hundred tests when he came back from costa rica because he didn't think to tell more than the triage nurse that he'd just come from costa rica. 4 months later, he saw a tropical disease specialist and was cured within a week (the open sore was tested for everything from infection to diabetes to allergic reaction to LOCAL parasites). BUT what if he'd never been to costa rica? What if a coworker/ friend/ family member had just honeymooned in costa rica, and he'd been infected? Would he even THINK to share that with the docs?
Part of medicine is also geography: My Uncle who has caught malaria a few times in his travels (malaria can always relapse, he was just spiffy enough to catch more than one strain of it). Suddenly collapsing at work with a *ridiculously* high fever and brought into the ER it didn't matter how many times he groaned for quinine, until my mum went in... they ignored him. The doctors didn't even know what malaria LOOKED like, they'd never seen it. However, if he collapsed in Egypt with a high fever the first thing the ER docs would have done is shoot him up with anti-malarial drugs. IN CERTAIN AREAS of this country, Lyme disease is an issue... in other parts it's never seen outside of medical school. In the "right" part of the country part of the questionairre determines if a person is out in the woods a lot. Ditto certain areas know to check deer hunters for the "human version" of mad cow disease (the human kind is also carried by deer... it's actually very hard to for people to catch bovine "mad cow disease", but as easy as catching a cold to catch it from a deer). But in my city, people don't understand hunting (it's just not common), so it's not on their radar.
Yet another example of "abnormal" is something known as referred pain. I have a friend who died of colon cancer because his shoulder hurt. It's called "referred pain". Meaning that the neural impulses get mixed up and while the PROBLEM was in his gut, the PAIN was in his shoulder. 6 months of physical therapy later he was in N stage, and it was too late. If, when the physical therapy provided no relief he'd had more tests, the cancer could have been caught. But he was a golfer, and the assumption was that he'd tweaked his shoulder. And it was also inflamed and somewhat damaged from golfing, so it was a good diagnosis. Just not the RIGHT diagnosis.(( A lot of patients get ticked off at tests that don't seem to relate to their problem, but doctors are VERY familiar with referred pain... so they often order tests that don't "make sense" if you look at a problem like it's the only possibility))
Refusing more tests just means you won't find out what's wrong. You'll either heal naturally, or it will become chronic but not dangerous, or you'll die.
Typically, when one of the options is death, I try to avoid it.