Same, I actually thought it was still ongoing at first because it didn't feel like much of an ending. But I might feel empty about it regardless at this point, the relationship felt like such a disaster and kept getting worse instead of better for so long. But that's basically what I expected since early on.
I think (and I don't mean this as a judgement) the author enjoys writing dark/unhealthy relationships and just didn't have much interest in getting the characters to a happier place and writing about that. So...it is what it is.

Why does finishing the last chapter made me feel empty? Like it left a hole in me. It felt like nothing was resolved and I just don’t know if I want more chapters?if it’s gonna be like this I don’t think they’re gonna last that long