Yea bro, I think what’s happening is that you felt so rushed to speak and pressured, that all your thoughts couldn’t be expressed at once. And it created a bottle-neck effect, where your words couldn’t be expressed quickly enough, so jammed in your brain and started stuttering for you. Add that with anxiety and the fact that you probably don’t even want to talk with them, and this just closed you off even more, furthering the bottle-neck effect. It could also be that you have a lot of repressed anger and it is all coming out at once and jamming your mental pathways for speaking. In that case it needs to heal, and you got to find a healthy relationship with your anger, so you learn ways of relieving it that isn’t repression. Your probably speaking before your brain can even approve of what you’re going to say, because the pressure to rush is getting you detached from your own feelings and emotions. And then the fear of being wrong in their presence is just making your brain overcorrect as a defense mechanism. So your brain is trying to shut down your expression because it rather feels safer to slow down and contemplate what you want to say in attempt to not be misunderstood by them. Also yes, sudden change of direction in topics or perspectives while speaking can definitely be hard on our body. Like trying to put a car in reverse while it’s already in motion going forward. Then when it’s going in reverse, putting it back in drive. This causes strain that sometimes our mind just doesn’t react to in a timely manner. I think maybe it’s best if you move out for now, find a therapist, and learn how to address this situation, even if it means no longer engaging in arguing with them. One tip I’ve heard can be really helpful is to argue through writing. So you get 5 minutes to write on paper, then they get 5 minutes to write on paper in defense. Then nobody can interrupt each other.