To be fair to the science, most tests are not that great—imaging is vague in which specific details it shows (e.g. for x-rays, all it shows it different materials that pass or reflect x-rays in different amounts—from which you can infer certain structures). Mind you, I have no idea in your case without being a physician myself and reviewing your case - I speak generally.

A common strategy is to use a first test that is ideally very cheap and high in specificity (true negative rate), but not necessarily high in sensitivity (true positive rate). That means that it'll tend to come back positive often and the doctor won't be sure you have a certain condition, but if it's a negative they're very sure you don't have it. It's a quick screening for the physician—"am I really obviously barking up the wrong tree?"

Consider that a test comes back positive, and it's known to have a 5% false positive rate. Suppose treatment is expense, is work for the physician to follow up with you over a month or two that could be spent helping other patients, and has side-effects with a non-negligible consequence on your health. Not to mention, if you still have the symptoms and you treat for the wrong diagnosis, now it's been days or weeks and you're back at square one, with a potentially worse condition (depending on how fast the condition progresses). That 5% is looking pretty bad.

Run another test that detects a similar thing in a totally independent way (this is an idealised assumption). Comes back positive, also 5% false positive rate. Since the two are independently verifying a condition through different means, ideally the false positive rate is now 0.25%. That looks a lot better.

Ideally, hospitals should have the resources to run a reasonable battery of tests, and the cost shouldn't be on the patient to allow the doctor to exert their due diligence in diagnosis. That's certainly a very ideal world, though, unfortunately—where in the US your care will revolve around money and insurance, in Canada, particularly big cities, you might find that hospitals and clinics just don't have the resources to help you quickly and the physician is still stuck in this dilemma on the basis of time/resources rather than the financial burden on the patient. (I do recognise that some doctors and hospitals will do way more than they need to get insurance money in the US, though).