I so could have written this post when I started therapy like 3 years ago. It pretty much mimics word for word how I felt about it at the time.
The first thing I'd say is, no, you are not wasting time. Even if you feel like you might be. The fact that you have started to recognise that you are consistently not making the most of your therapy is already an important thing for you to be recognising and thinking about how you might try to change this. Ultimately it is this type of reflection that your therapist is trying to guide you towards. It's not like your therapist has the power to make the changes for you, so it's not like they
do anything in that respect, they just guide you toward the type of reflection and give you an appropriate environment with which you can make those changes for yourself. Ultimately though, without that outside input that causes you to think a bit differently than you usually would, you might not get into that place of reflection and hence change, so it is worth keeping going.
Already you have recognised two really important things about therapy, which now it will help you to act on. The first is that you are not making the most of your therapy because you go blank about whatever it is you have thought about being important to say and have fallen back on saying the good things that you can think of. You have recognised that you go blank and you have identified some of your thinking processes that might be behind that going blank such as various fears both of her response and of how that response might effect you, questioning whether she could understand, feeling like what you have to say might not be important etc. I think these various fears and questionings are difficulties that we all struggle with from time to time. The important thing though is that we can't learn to overcome our fears without taking risks. We have to take a risk with what we say in order for us to recognise that whatever it was we fear might not necessarily happen or be true.
I've come to think of this hesitancy with saying stuff or just plain forgetting what you wanted to say as avoidance essentially. The most helpful things I've found to conquer it is to write a journal for my therapist expressing some of these things. I write about whatever it is I had thought to talk about but then know I will forget to mention. I write about however it is I'm afraid of him responding. I write about all of these things and then give it to him to read. It has helped decrease my avoidance of topics massively and it has helped with the therapeutic process a lot. I'd definitely recommend you try writing to your therapist and take it to session with you for her to read, even if you only take really small risks with what you decide to write to her initially. It will definitely help in terms of remembering more about what you wanted to say while you are actually in therapy.
The second really important thing that you've identified from your therapy so far is your responses to what she is saying. It's important that you communicate these responses to her in your sessions. If you feel like she is too expectant of you to give her a number or name
tell her that. Tell her that you don't feel like she'll believe you the higher the number you say. You can only resolve these type of tensions with your therapist by talking about it. It is more helpful to you if you learn to say, "I'm not comfortable telling you that because I don't feel like you'll believe me" than it is for you to respond in some other non-authentic way. If you tell her how you are feeling like she won't believe you, then she will have the opportunity to actually
address this concern of yours openly and that will actually help you in the process of your therapy. She can't do that though if you don't initially take the risk of telling her that you don't feel like she'll believe your number... Or telling her whatever else it is that you might need to about how you think she'll respond to whatever you might say...
Yeah so overall, even though you might not have felt like you have done much with your therapy so far, you actually have. It's already starting to help you identify your thinking and from there you will be able to decide to make some changes in responses to that. This is actually a really positive stage you are sounding like you are at that will most probably lead to a lot of growth. So don't give up just yet.