I think sometimes it is difficult to really believe that things are going well and there's nothing to worry about. I think of it as being hypervigilant, it's like you have to make sure to stay alert just in case so if she starts to pull away, then you can do something to correct the situation. It is irrational as I think abandonment fears come from the emotional part only, and it can't be thought into changing, if that makes sense.
You are still learning to trust, so what you are experiencing now is a part of that. It will get better in time, and when you do trust your T, you will know it. It is a very grounding feeling.
Thinking about you. Let us know how you are doing.