Need Help Identifying This BL Novel!

[littlelier]

I totally forgot about this novel and thought I could search it up, but I didn't find it(I think it's in my old computer where I lost the function before I could get out the files I stored in there. The novel is really good. At first I thought the title might be Highland Dragons or something, but it wasn't that one and then I research it on girded by looking at the list of dragon m/m novels, but I still find nothing. So, I'm asking you guys if you guys might know of it(or you guys know of how to find all the dragon m/m novel listed in this website):

The series setting is historical, the country had north, east, west, south, and center dragon guarding the borders, except the center dragon is the king. The king try to find mates for all the border dragons and himself. All I really remember is that the center dragon-king-had a mate who was his lover from the military time. Another of the border dragons' mate is that he and the dragons were mates too, but the dragon went home to tell about him to his family, but he got hurt in the head and forgot about his lover. Another of the border dragon is that after he got the mate he was convinced by his childhood nanny that his mate had the "fading disease" or something-it was really frustrating-this novel of the series.

So if any of you guys might know of this series, or heard of it, or know how to find all the dragons m/m novel from this website-please let me know...