Mycroft slowly starts to hate himself and starts insulting himself when he is alone or just in his head. At some point the mental hurt isn't enough but he can't get himself beaten since it would be to obvious, so he seeks out strangers who would fuck him roughly...

Bonus and virtual cookies for:
+ He pays to be insulted
+ He tries to do extremer stuff every time
+ He hardly can cope with people being nice
+ Sherlock worrying about his big brother

Extra bonus round:
++ Someone finds out
++ Lots of aftercare