Perhaps this will help for the first sentence:
In the 4th Century there was a monastic theologian named Evagrius Ponticus. He said the beginning point of sin is logismos. This is not an intellectual debate but rather a secret thought that has the power to stir the mind, a kind of secret dialogue. Demons fight by means of present things, objects that give rise to passions.
This seems to be what you're dealing with right now. Your thoughts make you no worse than an accountant who dreams of embezzling but doesn't. As you seem to have the strength not to give in to your fantasies, Continue, but ask God to at least give ease to your fantasies. And through fasting, which includes foregoing chatrooms et al where the fantasies are reinforced as well as cutting down on certain foods, you could find relief from the despair that your fantasies seem to bring you.