Ooohhh is the MC like a pharmacist in his past life?
I think so! Maybe!? Do you perhaps know the yaoi I'm describing with my horrible memory? ╥﹏╥
I don't know if this is the exact manga but it has the same kind of plot in most ways:
https://www.mangago.me/read-manga/when_i_tried_to_enjoy_the_life_of_a_neglected_husband_i_ended_up_taking_the_route_of_affection/
OMG I LOVE YOU. THIS WAS IT! THANK YOU
You're welcome
I give up searching and still wish I had my old list of saved yaoi/bl(s) but anyways it's a yaoi where the mc may have been reborn as a character that died by the ml i think (pretty sure reborn in a novel.. Idk). It's a colorless yaoi and I remember the ml already had a male wife with long hair, yet the ml instead obsessed over the mc and only has sex with him instead of killing or ignoring him. That's all I can remember and goggling it doesn't help!（/TДT)/