First of all, I applaud your courage and honesty.

Having spent 5 years in therapy for my marriage (20 years at the time) and literally in the process of ending it at this very moment (after 30 years) I feel for both of you. Based solely on what you wrote I'd like to ask the following if I may:

1) Does he feel the same way about you that you feel about him?
2) Does he know that you are having these insecurities?
3) What was the basis for your initial attraction? (looks, sex, character, and so on).
4) Are you willing to commit to him and not just the one you've come to know over the past 6 months?
5) Can you believe that this has great potential for a long term relationship?

These are basic questions that may help you to find resolution. I would be willing to share my answers to these questions if that would help with insight.

Please keep in mind that issues of mental health are only beginning to be understood. So opinions will vary, even among psychiatric professionals. What's important is understanding what's effective in helping you to resolve these issues. Then and only then can you truly enjoy your relationship fully.