Catnapper,
one thing is being shortsighted, the other thing how well it can be corrected. I am -7/-6,5 dioptries- bad enough for all these nice high index lenses that let my glasses look much thinner.

When I was younger, the correction was better than 100% (with 100% they describe an average capability of view, so this means after correction by glasses my sight was better than the average), now as I am being older it is 90-100%

If I was you I would take my notion seriously and ask my doc to look into it more and not just measure the dioptries. E.g.

as you grow older, you get long-sighted as well. This can overlap your shortsightedness in a strange way. I know you are rather too young for that, so it's unlikely. Which doesn't mean impossible.

next: the capanility to see in the night depends on your eye background and can be checked by dropping a med in your pupil, so it gets large and the doc can inspect the eye background. Has this been checked by your last doc?

Third: there are things like cataract and glaucoma - ask your doc or google about it in detail. Cataract happens to older people more than to younger but my doc says he has seen it in people under 30 as well. There is surgery available (it's not complicated for eye doctors). I have one in an early stage, too early for surgery. One of the symptoms is that you have problems driving by night because the lights blind you more. Glaucoma has to do with the eye pressure.

Forth: Is your retina ok. It can get holes etc, especially with very shortsighted people. This can usually be fixed with laser.

It could also be a stress symptom. I think it is very important to describe what you see in detail to the doc: when do you notice it, how long do you have the notion, etc.

Last, and unlikeliest but not least: 10 years ago I had a brain tumor that I noticed because the eyesight got worse(on one eye it was down to 30%, on the other one at 60%). I don't want to worry you- your symptoms do absolutely not look like mine- on the other hand the normal eye doctor found nothing and sent me to an university clinic. They said the same symptoms could also have been started by an infection of the optical nerve- so this or many other things could also be a reason for your problems.

Please I don't want to worry you (I had surgery and it is amazing what they can do these days) but I would not just be happy with the check of the glasses.

Good luck