I am definitely heterosexual. I've always desired females, despite having factors in my background (Distant father, dominating mother, and older sister as only sibling) that many would say predispose me to homosexuality.
I just get the impression from reading you that you are trying to convince yourself that you are not gay.
As for what predisposes you to homosexuality, no one knows and I think it's best not to try to figure it all out or make assumptions.
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J'ai juste l'impression en te lisant que tu cherches à te convaincre que tu n'es pas homosexuel.
Quant à savoir ce qui prédispose à l'homosexualité, personne ne sait et je pense que c'est préférable de ne pas chercher à tout comprendre ou à émettre des hypothèses.