I got that feeling right now. It's creepy.
If it's just a feeling, then sometimes paranoia is natural.
If it's more than just a feeling, call the cops. Or if it's not a really really serious situation, call non-emergency. Or a friend.
Yes, I'm being stalked by my best friend's ex.
Male or female ex?
Yes, I'm being stalked by my best friend's ex.
Male or female ex?
Female.