It often takes me at least 4-6 sessions to get to know a T enough to decide if I want to continue with them long term. It usually takes about 6-12 months (of weekly appointments) to get into anything very deep/hard. I'm slow to trust.

Do you have any sense of if this T is someone you could grow to trust? As others have said, there's nothing wrong with trying someone else. That said, I think there's also a period of time especially early in the relationship where the T needs to get to know you (I sometimes call this, jokingly, "training" the T). In the vast majority of cases I suspect it takes time before you can really open up to someone (and that's probably healthy, to some extent).

But it is your choice. You can decide now or at any point in the future that it's not working with this T and stop seeing them for whatever reason you want (including "I just don't want to anymore").