It definately could have something to do with stress. Stress affects our bodies in so many different ways, but you typically start seeing issues with the immune system if stress goes on too long. Do you see a correlation between your stress level and when the styes show up? Do you by any chance change your eating habits when your stressed, or get tired and rub your eyes more often? I really don't know about scar tissue forming. I am wondering if you are actually getting completely rid of the styes inbetween outbreaks, perhaps there is some lingering irritation there.
Maybe you could do some relaxation techniques to help combat your stress? Of course when I'm stressed is usually the time when I have the least amount of time for myself
! But it is so important, if only 10 minutes before bed, it'll help you sleep well too.