It can be hard. I spent many sessions saying "I don't know what to say." Sometimes saying that is the beginning.

Don't put blame on yourself though. It isn't about blame. Perhaps she is giving you the room and time you need. She knows that it is hard for people to open up. She knows that not knowing how we are feeling can be reason itself to seek therapy.

Just tell her how hard it is for you to "open your mouth" and let her help with it from there.