According to Osho, it is simple: repression shows up as sexual dreams and fantasies you cannot avoid; transformation ends them. A truly meditative energy remains unprovoked even amidst temptation, as in Buddha's monk who uplifted Amrapali, while the repressed are 'sitting on a volcano' and easily fall. So check your nights and your spontaneous responses, not moral effort, for the truth.
If you still dream or daydream about sex, it's just pushed down; if those stop and you stay calm even when tempted, your energy is transformed.