Oh, and here's a list: https://www.ereads.com/best-sci-fi-romance-books

You might have read one of these, and thought it was either sf or romance. Probably my two favorites on the list are Shards of Honor, by Lois McMaster Bujold, and Gabriel's Ghost, by Linnea Sinclair. Although I liked the original better than the revised version. I can't count how many times I read Shards of Honor... 7? 8? I probably read Gabriel's Ghost 4 times.