I was always told if you don't wear glasses the number will go up, but i'm not sure it's all true.
I think (this is my opinion) if you have those ranges, it is very unlikely you will go very high, because myopia is genetic (i inherited it from my father). Usually the worst cases of myopia start when you are a child (my brother started at 7, he was almost -10.00 when he had his lasik surgery, I started at 9 and I was almost -8.00) we couldn't see much without glasses ( I couldn't read a book or watch tv without glasses)
since you don't like to wear glasses, you should considered contact lenses. I hated glasses myself, and rarely wore them, so I feel your pain. I know you might not need them for some occasions, but if you are going to be in a classroom or somewhere where you need to see distant objects, you are going to need them.
Also once your problem stops advancing you might want to consider lasik surgery with a good doctor, not just any doctor. I know some people had some complications but no one in my family had. The recovery time is only 24 hours.