Hi TBF,
What you're describing is sometimes referred to as cognitive impairment, or the cognitive effects of anxiety and trauma–in this case, mixing up your words– and it is a very well known and common phenomenon.
It's great that you've made an appointment with your GP, because although I doubt anything more serious is going on, it's always a good idea to be vigilant about changes in your thinking or functioning that don't seem quite right to you. I'm not at all a neuroscientist, so this is a bit of an armchair guess, but I wonder if singing uses a different part of your brain that is less affected by your anxiety?
Again, not being a professional, my understanding is that mixing up words is a fairly common kind of "brain fart," and that because you are not forgetting words entirely, slurring them, or thinking that you are saying one thing when actually saying another, and because you feel otherwise healthy, you have little to be concerned about.
In any case, be sure to mention all this to your doctor, including your anxiety and your concerns.
Finally, and most importantly, are you able to get help with the domestic violence issues you mentioned? Making sure you are physically safe and in a sound living situation is the very first and single most important thing you can do for your overall health, and your cognitive wellbeing as well.
I am not very familiar with what resources are available in Australia for domestic violence victims, but hopefully you are already aware of some or someone more familiar can chime in below.
Please stay safe, take it easy, and be well.
Warmly,
Aaron
