Paranoia

I feel like im being stalked by someone i dont know who but it started with a note on my desk saying “i love you” and its not from my girlfriend because i go over to her dorm she doesn’t come to mine then the next day i see on a note on my window saying “you cant ignore me forever” and at this point im genuinely concerned i asked my girlfriend she denied to doing anything and 3 days after that (currently) i find my window open when i know for a fact i didnt leave it open (luckily my dog and cat didnt jump out) and now im genuinely concerned for my safety and my pets safety im thinking of getting a camera or asking a administrator to see the cameras