I admit to having the same problem. First working out what I was in the beginning, and even now working out what my gender is on any given day. I still haven't really worked out exactly what gender truly is, but i know what works for me and I'd like to share it, as weird and unscientific as it is. No idea if it will help at all
I literally just try out saying aloud(alone) or in my head, different genders. For example "I am a demigirl", and invariably i get a rush of emotion, I will involuntarily smile if it just feels right and I'll frown and feel grumpy if it isn't true. I find it takes me out of my brain and lets my gut instinct take over.
And to you, or anyone who is unsure, remember there is no wrong way to have a gender(or no gender)
Sorry for the unsolicited advice. I thought I'd just share what works for me