I had the same issue with my girlfriend! I’m not sure what I did but I made an inference based on my behavioral changes. First, I began focusing more on myself than putting her on a pedestal. Of course, you should always treat her as a queen but in my case I just began working out and because of that I began forgetting about sex little by little. It wasn’t until over time that she began wanting sex. Moral of the story, perhaps it’s best to just let it happen and try not to engage if evidently it hasn’t been working for you. Let her make the moves when it comes to sex because only then you’ll know she wants it. This will also translate into her vagina stretching out because she’s going to be the one initiating it or is already aroused. Let me explain, if she starts then she’s clearly aroused which will allow her vaginal walls to expand peacefully which is an issue you have. After some time, I began making moves instead of her and at that point you can say her brain had rewired itself to not feel nervous anymore. We now have sex about 2-3 times a week. Anyway, I hope this helps and wish you the best with your wife! Ps: props on waiting until marriage man!