I have this also, that I have had thoughts recently, after talking about stuff in therapy, and I'm not sure if they are memories or just imagination.
My t says listen to your body, it never lies. So if you have a somatic, body response (maybe shaking, going cold, feeling sick, pain etc) that is your body's memory.
Yes, I am finding that I have more of these thoughts the more therapy I have. It is destabilising, and I sometimes find I am wobbly for a few days after a session. I guess in the long run it takes the power away from those thoughts and feelings and leaves us less vulnerable to them, which is good, but in the short term it is hard work!
Xxxx