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Let me see if I can help here...
I have read your post a couple of times and I think I can answer your question.
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Oh, OK... I can see you are offline. Let me go ahead and see if I can help with what you have provided up to this point.
Well, let me start by saying that you shouldn't beat yourself up too much over this. Given the fact that your trust has been betrayed in the past, it is quite understandable that you would react in the way you did.
It is important to point out that it speaks to how much you care for this man that you were so "afraid" (for lack of a better word) that he was betraying your trust. If you didn't care, you would not have reacted in such a manner - it wouldn't have matter as much you see.
Now, having said that.....
Your question is how to rebuild trust - and this is a GREAT question :)
I would start by telling him that you respectfully XXXXX XXXXX terms of it being a "no biggie" as he said.
Tell him how important trust is for you and that you have been hurt in the past, but you want to be in a relationship in which both of you can trust each other.
I would also share this conversation with him (this one that you and I are having) you can go back and look at it anytime on the Just Answer site - this will help him understand how important trust is to you and how important it is that he truly forgives you as opposed to it being (again) "no biggie".
Finally, I suggest you pick up two copies of a book titled The Five Love Languages by Chapman. This is a wonderful book for any couple and I think it is especially a good choice for you two. This book will help you both understand what is important to yourself as well as your partner.
I hope I have answered your question. If you need clarification please just post a response here and I'll be alerted by email and get back with you as soon as I can. However, if you are satisfied with my efforts, please don't forget to click on the green accept button because I need to get credit for my work. I wish you all the happiness in the world.