Record and/or document all times and events meticulously. Do not react or respond in any way...even a negative response causes a stalker to experience pleasure. Give them nothing and hopefully they will move on to another target. If you decide to report to authorities this may cause them to become incensed and hostile, as you have introduced a third party to their game, the invasive actions may escalate. And yes this is a 'game' to them a 'power' game they have created to distract themselves from their meagre existence. you react...and they get their little win. Pressing charges is a long arduous painful process...unless they have physically harmed you, threatened harm, or crossed any other unforgivable personal boundaries...let it alone. As a victim with experience of this type of crime I have stories that would make your hair turn green...document, document, document, is my best advice.