So how do I explain pansexuality to my girlfri…

So how do I explain pansexuality to my girlfriend, I've tried but she still thinks it's just a preference and can easily change and nothing I say changes her mind, I don't know what to do or say that would work so I need your help…I want her to understand who I am

sorry this is so late!! i’m not sure how to answer this, so i’ll toss it to the masses, if that’s okay 😀