that's all tied to the Inhibition stat (click on the female image icon, below where the weather picture and current time are, and then click on the Skills link - it should be at the very bottom, under Sexual Skills). if you didn't start with the slut or gopnik background, it's gonna be pretty high. you can temporarily lower it by becoming an alcoholic (getting drinks from NPCs or buying wine at the grocery department of the supermarket; if you go this route, your character can feel fine with wearing more revealing clothes for a little while until the alcohol wears off), or you can permanently lower it by doing actions that lower your inhibition (flashing, teasing, having sex, etc.) it's a bit of a grind, but it goes quick if you keep buying wine and getting laid as much as possible.
