whenever i plug in my laptop, the screen sort of flashes? not compeletly black or anything, it seems like the brightness just changes frequently (very frequently) and it really hurts to look at it. It only does it when i plug it in though, not when its unplugged. It did this back in august but it stopped for a while and it started around a week ago. I really dont want to sent my computer to a specialist so are there any tips for fixing this? thanks!