Because you have now opened up, it means you get the bodily response that did not happen when you were shut down. Your body is going into fright flight mode. It's like you have all the emotional pain dammed up inside, when you start taking about the rape it puts a hole in the dam but instead do trickling out so you can deal with it, it comes out in a huge rush because there is just so much pressure there.
Like Harley47 said it will lessen with time and management. You need to find what works for you.
I have this happen a lot and I am going to lay myself open to ridicule here by telling you that I talk to my inner child, I explain to her that this is a stress reaction and that I have it under control. That nothing is going to happen to her now. I talk myself down in other words. It works for me.
You are best able to find what works for you.