My face is fairly symmetrical, but sexually I don't feel more active than others. And if my face is asymmetrical, does that mean I'll have fewer partners and weaker desire? I want to understand how much appearance actually affects this.

Based on the material, initially women with more symmetrical faces were indeed found to have slightly more partners per year and slightly more permissive attitudes, but the correlations were very weak. As soon as scientists took place of residence into account, these effects disappeared completely — that is, facial asymmetry by itself decides nothing. Everything that looked like a connection was explained by environment and life circumstances, not by facial features. So there's no point in looking in the mirror for an explanation of your sexuality: it is influenced by relationships, environment, mood, health, and upbringing. If something is bothering you in the intimate sphere, talking to a doctor or psychologist would be more useful.