If you are suspicious about your symptoms then it's worth checking out.
Probably get your doctor to order you an ACTH stimulation test. Sometimes this is called (depending on what country you are in) a Synacthen or a Cortrosyn test.
The hormones parameters that they must include in your test are: cortisol level pre and post ACTH. 17-ohp (17 hydroxyprogesterone) and possibly 17-ohp (pregnenolone), your testosterone levels and possibly your androstenedione levels also measured both before and after the ACTH.
If they miss out on the 17-oh progesterone level then it makes the testing a virtually useless exercise. It must be included to diagnose CAH.
The problem is some doctors get very defensive if you come in with a list of what you want to get tested, so you need to be strong and say that your niece has just been born with this and perhaps it may make sense of some of your lifelong symptoms. Don't let them put you off and be very specific about what needs to be tested.
DNA testing is also very diagnostic but expensive. It also doesn't tell you exactly how the disease is being expressed in YOUR body quite as well as an ACTH test, but it would tell you what mutations you have with their anticipated effect.
All the best. Let us know how you get on.
