Did you build your character for Stamina and Energy? If not you're going to have a hard time, especially if you're on a harder difficulty. Endurance, Mind and Dex are what you should focus on so you have the reserves to survive gangbangs and your sex acts take less energy to perform. Also don't neglect bonuses from the Shop and Meals, as well as the buffs from being Well Rested (don't go to bed horny or after being raped into unconsciousness by the guards).
A lot of the games stats are percentage based so you can quickly stack up some insane numbers but don't neglect your Passives either. Getting semen fired into your whore holes enough times will eventually give you Energy Regen when it happens, meaning you can melt your brain with orgasms and gain back the Energy you lose while you do it. Slimes are good for training that, since they go multiple rounds on you and make you air tight while they do so.
What is your level/stats like and how many passives do you have? I can grind the Yeti boss out with my Karryn, see attached.