Hey! I too can relate to this. It does take time to really start to open up. As said above, letting your therapist know about this is a good way to start, they're then able to reassure you and help to hopefully make it a little bit easier and comfortable for you.

The thing that helped me, was writing the stuff down that I needed to say. You then have the option to show them what you've written or read some of it with them. Even if you just acknowledge to them that you have brought with you some notes, that might help the process, and ease you into eventually revealing whats on the paper.

I hope you're able to open up a bit more soon! It's a daunting process, but ultimately, will provide you with some relief and the support you need