can only remember the quote: “I go where you go”

This has been driving me crazy for weeks. All I remember about this film is that (and I’m fuzzy on the details) is that there’s a guy who’s following around this girl from his past. Not sure if they were exes or just childhood friends. She thinks they sort of serendipitously ran into each other but slowly comes to realize he’s actually been stalking her and following her around. She calls him on it, and he’s iirc not all there, and he doesn’t understand fully that what he’s doing is wrong. He tells her that he knew/saw xyz thing because he “[goes] where [she goes].” like this:

her: [something to the effect of “how do you know that?”]
him: i go where you go
her: what do you mean you go where i go?
him: wherever you go, i go there
her: you can’t do that anymore. you have to stop going where i go.
him: why?!

i know this is probably a long shot, but if you have even a vague guess, let me know!!