When will my vision stabilize?!

I'm 18 and a senior in high school. I wear glasses pretty much all the time, once in a while i'll take them off or forget/ temporarily misplace them lol. My prescription is Right -5.50, Left -4.75, and I have a -1.50 astigmatism in both eyes. All in all, my unaided vision is pretty terrible. I had my last exam about six months ago. I got a new, higher, prescription, high index, high optic lenses with all kinds of coatings lol. Recently though, I've had trouble seeing the board in class if I'm near the back (20-30 feet away maybe?)I usually can make out the words though. However, One class, in the very back with small font, I couldn't make out the words at all I might as well have not been wearing glasses.

Is this normal? Up until now, I've been told my eyes were normal, just highly myopic.
Assuming this is normal, which I imagine it is and my eyes are just changing, when will it stop approximately?
Also, I heard that contacts can help vision balance out. I never really minded wearing glasses though so never even tried contact lenses. Is there any truth to this, and would it beneficial for me to try them?
Also, if you can guesstimate, what will my prescription/power/visual acuity be when it levels out? Like how much worse can it get