So I went to my optometrist (about half a year ago), explained the problem, and asked them to check my eyes. We've been going to the same people for years now, and they always gave us good service and good prices. They checked my eyes, and told me everything was fine. I still felt something was off, but what could I do? I left.
I didn't do anything about it for a while, but my eye kept on bothering me, and I didn't want to go back to them because I didn't want to be told it was nothing again. Finally on Thursday I went to a local university, where the optometry students will do eye exams for free, and because they're learning, do them from the ground up. I figured they would be able to figure out what was wrong.
Now, let me say that my eyesight isn't particularly good - my glasses prescription is -5 on my left eye and -4.5 on my right.
The optometry student checked everything out, figured out how much I need to be corrected - and when she saw my glasses' prescription, both her and the doctor's jaws dropped. Because my real prescription is -4 in my left eye, and -0.7 in my right. No wonder my eye was giving me problems! The lens was off by four dioptre! (to be fair, my number went down, it's not that it was always like that)
In short, when people complain their lenses aren't right, PLEASE LISTEN TO THEM!