However, after waiting so long I now feel as apprehensive as she does about sex. I don't want to make a mistake and ruin what we have just to quell these urges. How can I be sure that the time is right. Actually it is not a problem at all. In fact, intense sexual desire is healthy for a healthy monogamous relationship.
Sex is just that, sex.
It takes almost nothing more than physical arousal to have sex. You have both shown that you are capable of waiting until the time is right. Casual sex can be great fun, but it can not replace the uniqueness and oneness of making love. The union of two people in love should be special. Building a loving relationship requires time and patience.