As for the sex stuff. For women a lack of trust can affect the experience. She displayed this early on when visiting at not being able to get into the mood. Not being able to climax in certain positions could be another presentation of this. When she feels in control she is able to climax. As she comes to trust you, it may change.

I don’t think it is about her lack of experience, or that it says anything about your performance. Just a symptom of the trust issues.