Any more clue you remember? Like was it manhwa/manga/manhua? And what's the uke and seme like, etc?
Manhwa, also I believe the uke thought that the seme was dating a girl but turned out to be wrong, and I believe the seme was also a professor at a school the uke went to
Maybe this? The characters on the cover are not the main characters. https://www.mangago.me/read-manga/between_coincidence_and_inevitability/
YAAAAA THIS IS IT TYSM
If i remember correctly, the seme let the uke live in his house because it helped him work better, also the uke had a bitch ass ex, it is also completed, I thought I had it on one of my lists but I guess not