This is a black and white manga where there is a husband and wife. They haven’t had sex for 3 yrs or smn. The husband and his co worker made a deal cause the husband gets off on his wife having sex with the co worker or something.

Kekkon 3-Nenme, Netorareta Tsuma ni Koi wo Shita.?

http://i.imgur.com/LxhWm.jpg (will reformat this some day…)

No..this is not it sorry! But thanks for replying^^

Of course, I could be wrong, but somehow your description reminded of "Nande Koko ni Sensei ga!?" (Why the Hell Are You Here, Teacher!?), also known as "Golden Times."

Don’t believe in the me that believe in you, don’t believe in the you that believes in me, believe in yourself who believes in you!

That’s not it either 😭. Something else I remember is that the wife did not know the husband and the coworker was in on it. The co worker actually forced himself on the wife while the husband was sleeping / distracted(?) or wasn’t home. The wife does find out about it at the end. Also thank you for replying!!