Welcome to the forum Lhouse93
Sorry you have to deal with incontinence at a young age, wearing a thicker plastic backed diaper like dry 24/7 or Betterdry (my diaper of choice to manage my OAB bladder issue) will help give you more confidence as you can trust them to do their job and with the added capacity you will have to change less often.
if 5 years of wearing no one has noticed or said anything about my diapers just 2 people mentioned my need for a back pack when I head to the bathroom.
The test your urologist wants to do is quick and easy but there is a slight discomfort when the camera enters the bladder but that only lasts a few seconds (at least it did for me), the test may not lead to a cure but it will give your urologist a clear picture of whats happening and will help her to rule out some life threatening issues.
Ive had the test done twice and will probably have a third in a year or two, and cant recommend the test enough to help figure out what’s happening and to give you peace of mind.
Unfortunately you may never be free of diapers but with a diaper you can trust managing incontinence issues
does get easier I skipped the meds my self as I really don't want to deal with any of the possible side effects and if they only reduce the issue why bother taking the risk. Thicker diapers are not noticeable with the correct clothing and they give you peace of mind when you have an accident that they will do their job.
my view is a thicker diaper is less noticeable then wet pants when a thinner more discreet diaper fails

we all dislike being back in diapers but life is not that bad in them its just more challenging.
hope you come to terms with your issue and get some better protection. there nothing to be scared of when getting the test done as its done all the time and is well worth it.