coco, welcome to the Psychotherapy forum at PsychCentral!

If you've been going to therapy for a month, that is only about 4 sessions if you're going weekly. That is not long at all. It takes time to build trust with your therapist and create a strong working alliance between you, one that can bear what you have to share. Your therapist may be ready to hear what you have to say, but you don't sound like you are ready to share the big thing you are "hiding." It's OK. That is normal. What you can do is start small, and share a little bit of something here and a little bit of something there. And you can see how your T reacts and whether she proves to be trustworthy. If she can handle these small things and react favorably, then you will come to trust her and eventually be willing to share the big thing.

In my third session with my therapist, I so wanted to share this big thing with him, a big shameful thing from my childhood, a whole slew of forgotten memories that I had remembered just the week before out of nowhere. We spent the entire session just sitting there with me unable to tell him, even though I wanted to so badly. We just didn't have the trust or relationship for that yet. He understood this, but I did not. I remember at the end of the session, he said to me, "I want you to know I respect your ambivalence about telling me. It's early yet. You don't have to perform when you come here." Those have been strong words for me, that he respected my ambivalence, and would be patient. We spent the next few sessions talking about this and that, building trust, learning about each other. Then when I was ready to tell, I did.

Wait for when you are ready. If T is pressuring you, ask her to give you some space. And tell her you are terrified.