When i was in highschool i had a stalker. Nowhere near as persistent or scary as what you are describing. Feeling watched all the time is a very nauseating feeling. At some point i confronted him about it. He didn't say anything. Just mumbled something for a second and ran away. Haven't seen him since. Not going to help you, i know, but maybe it makes you feel a little better that you aren't the only one who experienced something like this.