Nick I know how you feel. I'm about 8 1/2" length and 5 3/4" girth. However, I've had similar complexes, to the point where it really irritated her and was a turn off. I've made comments in the past such as I was getting surgery etc. just to get feedback and she told me if i do she would not sleep with me because I'm already too big. She has told me several times I was big. She's showed me that by her actions in bed, the pushing back, limiting our positions, screaming, cumming, at times her legs are shaking, saying that i'm filling her up, saying that I'm so long, grimacing even when she is drunk, stoping me from raising her legs.
Men always want bigger but most women could care less. Whatever the case may be, listen to your wife, learn to please her. Focus on making her comfortable and making love to her and pleasing her. Don't try to hurt her, dont try to make her sore for 2-3 days afterwards, it only hurts your chances of having sex more frequently.
The only way to cope is to accept what you have. You can't change it. There must have been something that happened in your past to make you feel the way you do. Deal with those issues and just know that if your wife enjoys it you shouldn't ruin it by constantly asking if you are big enough. Being unconfident is a huge turn-off. Show your confidence by your actions and your words. You will get alot further in your relationship.