The "God called me" moment. What makes you so certain you got called to do so? God won't allow you to be tempted beyond your capacity, so either you can overcome this, or God didn't call you to be celibate at all. But in the chance that I am wrong, and God did call you, and you simply need direction in controlling your fantasies and whatnot - I will suggest what i usually suggest to issues on lust.
Make a complete shutdown of all avenues that the enemy can use to tempt you. Television, magazines, posters, even friends who discuss sexual topic. It must be complete. You will be tempted to return to your old ways many times, but you must steel yourself never to do so. Sometimes, the enemy will tempt you the strongest during these times, for in the same way Christ fasted before his service, so too did the enemy tempt him three times.
Now, this is not a permanent abstinence, only up to a time you become able to control your urges properly. This is the reason for most abstinences and spiritual fasting - to allow ourselves better to resist the demands of our physical body. Aside from that, such abstinence must be accompanied by spirituality and prayer and meditation. It is done regularly even by New Testament Christians, and as such, is still practical for use among us believers. Once so refocused, you'll be able to tackle it better.
