Additional tip: try this approach with people who are as close to "safe" as possible at first. Instead of saying "no worries" next time, actually allow yourself to express discontent to a friend who is disrespectful of your boundaries. Start small and do it when you are in a decent place mentally and emotionally (as close to it as it gets).
Assertive communication can be really difficult if you are just starting on your CPTSD healing journey. Please have compassion for the part of you that's terrified of standing up to others. It's afraid for a reason, and it's trying to sound an alarm and protect you.
Thank the fear, feel the fear, and then do it anyway.