Do you maybe mean "Every Breath You Take" by The Police?
That's a common answer to this kind of question. A lot of people think of it as cute and romantic at first, but the song really talk about the Big Brother (from George Orwell's 1984): a state of constant surveillance watching "every breath you take, every move you make".
Since you've gone, I've been lost without a trace
I dream at night, I can only see your face
I look around, but it's you I can't replace
I feel so cold, and I long for your embrace
I keep crying, baby, baby please
Oh, can't you see
You belong to me?
How my poor heart aches
With every step you take?
I understand the full lyrics, but most songs generally default to romanticism. If you're not paying attention it's easy to misinterpret.
Yes that's the one I'm talking about. I could have sworn I heard an interview about him talking about how it's about someone stalking a former lover. Memory is weird that way. You're interpretation is probably the one I'm going to go with from now on though I like that more.
I could see it being a bit of both. Lyrics are often inspired by something and describing something else. In this case, someone stalking a former lover could be seen as "going full 1984's Big Brother" on them... and it makes sense with the whole romantic mood that the song has: the stalker sees themself as romantic and sings it that way, but when you look closer you realise it's actually very creepy.