I'm genderfluid and I have a system where I put down a letter on the whiteboard I have on my door and that means a certain set of pronouns and my "friends" said they'd follow whatever's on the board but they keep misgendering me so I've been avoiding them but now they're pestering me because they think I'm being petty - am I just making a big deal out of nothing?
No you’re not. Explain how you set up this system because your gender is important to you, and that by misgendering you, your friends are disregarding not only your wishes but also your identity. Ask them how they’d feel if you started calling them a boy if they’re a girl or vice versa, and how they’d feel if they asked you to stop but you didn’t. Explain that you know it’s hard to always use the right pronoun, but using the wrong one hurts, so could they please make an effort. If they still misgender you, I suggest that you avoid them, and if they start to pester you again, tell them that you already explained why you’re avoiding them. You are absolutely not being petty, being misgendered doesn’t bother some people, but for others, it really does. You shouldn’t have to stick around people that ignore your comfort and your identity.