http://www.mangago.me/read-manga/doutei_sama_no_omou_ga_mama/
try reading this
Asexuality is lack of the sexual attraction, however, you can still have feelings for someone.
BL doesn't mean only yaoi and sex, however, audience is far more into sex, or the story where the couple will eventually have sex even if it's not shown. I doubt there are BLs with accurate asexual representation (there are maybe some where someone "cures" the asexuality).
I do think there are some mangas that explore gender/sexuality in a different way but they are not really your usual BL.
This article may be very useful, maybe you will find something nice to read?
https://coherentcats.com/2019/06/03/asexuality-in-manga-and-more/
Also, I think this was about asexuality as well but it’s been a really long time since I read it so I’m not sure..
http://www.mangago.me/read-manga/sexless_am/
can you guys recommend me bl that contains asexual relationship please, ive never read one