How long before he grows tired of dealing...

Why is it that no matter what I do I can't shake the fear? I am happily engaged to a great man but yet I am so insecure about things. I am afraid of him cheating on me, which I know deep down he would never do, but I still catch myself checking up on him and questioning little things here and there. He understands why I do it, but I dont want him thinking I dont trust him. If we argue and he raises his voice, I shut down and start to cower in fear. I am tired of making him pay for all the things that happened before him, which is what I feel like I am doing. I am blessed that he is so understanding and deals with all this without question, but will it all eventually end, will he get tired of paying for someone elses mistakes?