i was playing wow on a ptr and a little message popped up saying i was using like third party stuff, which i wasn't and then my computer turned off. Then today i played on the regular server for like 5 min then got kicked off and was told i was banned when i logged in on the wow website.

If you honestly were not running anything, you may want to run a virus scan of your system. Take stock of anything that you had running at the time because Blizzard picked up that there was something suspicious running at the time that you were playing (they do monitor to that level)

Even when playing on the PTR you are bound by the TOS. so yes you can be banned. But if you were doing nothing wrong you can appeal the ban by contacting blizzard directly. Just be cordial and you should be able to get your account back in a decent amount of time.