Was there context in which this was said?
If a T just popped out and said that out of the blue, I would feel confused. I would, however, ask for clarification. That's why I agree with the others who have said you should talk to your T about this. Any answer we give, as we are not mind readers, could be way off the mark.
I will add, that my T did say something similar once. And we'd been together longer than 6 months. There was context for her comment. Basically, she was telling me I needed use my words. That she couldn't read me and know what was going on. I found it both reassuring and scary. It was reassuring because it confirmed my experiences with her and others. where I feel like I'm broadcasting my thoughts and feelings but really I'm hiding what's going on. Also, it was reassuring because it showed she really wanted to know. She wanted to get past the facade. The scary part was that she couldn't magically know what was going on. She couldn't just fix me. I was going to have to find a way to open and share what was going on inside of me.