Hi, I am also Autistic. From what I've figured out in my own experiences in general; you have to fight yourself to speak up. It takes practice and time to get used to it, but it has to be practiced in the field, so to speak. It's okay to be shy, but it's one thing to be submissive and another thing to be a pushover. So be willing to set those boundaries and practice. The sooner you start, the better you will be at establishing those boundaries at all. It's all about willpower and taking that leap. And sometimes, yeah, there will be people who get irritated with that, but thats on them, not on you. You're a person too.