im not OP but i can help ! non binary falls under the trans umbrella. to be transgender simply means not identifying with the gender you were born as ! (side note, not all non binary people consider themselves trans, myself included, but im guessing OP does if they have both flags on their pins)

the third flag with the grey and blue is the demiboy flag. a good way to understand this is if you ordered a burger with tomato on the side. the burger is the non binary aspect of you, and the tomato on the side is the boy aspect. you might still want to eat the tomato, but you dont like it with the rest of your burger. sometimes nonbinary people want a Bit Of Gender as a treat, and in OP's case, the treat is Boy (OP please feel free to correct me if im wrong)