First of all, discard the notion that an orgasm is something that you have that you proceed to "give" to your wife. And, don't worry, your size is perfectly a-ok, the problem's in your brain, not your dick. The more pressure you put on yourself to perform so perfectly that she has some ideal orgasm the less likely it is to happen. Instead, take pleasure in the fact that you both now have the chance to explore and discover what it is you both like.
It's obvious the great deal of affection you have for your wife, and I really think that's great. So just cherish her, hold and caress her, ask her what sexual fantasies she has, explore her body and find the places she responds to, give her a back rub or a foot massage before sex, kiss her passionately and accept the fact that she may not have an orgasm but that's okay for now because what's important is the fact that you are expressing to her how much you love her.
Sorry if this post sounds like some cheezy 70's sex manual, but I've had a couple of anorgasmic lovers and I can tell you from my experience that this worked for them, both of whom eventually became quite ardent.
All the best to you and your wife :smile: