I am trying to find a manga where the uke is the scenes assistant or secretary or something and the seme is a womanizer or at least switches partners constantly? This annoys or concerns the uke and he complains and I think the seme tells him to replace his lovers but it could be the uke who offers -_-'

Anyway I am sure that the uke is sure that the love is one sided and gets upset and stuff. Thanks for helping sorry I am so vague it has been a while!

Each of these has elements of the plot that you detailed, but they also differ in some respects. The story you are seeking is probably not among them, but perhaps you'll enjoy these, as well?

Hisho wa Shachou ni Kudokareru by Takakura Tomoko (Chapter 1)
Hisho to Yajuu by Takahashi Yuu (Chapter 2)
Ruriiro Butterfly by Fujikawa Ruri (Chapter 5)