According to Osho, losing interest in sex is a natural outcome when repression and taboo drop: much of sex’s thrill was your own fantasy created by prohibition. Once fully accepted and easily available, its mechanical repetition shows and boredom arises. Don’t revive it through borrowed repression; recognize conditioning at work instead of feeling guilty or ‘sick’ about the change.
If sex stops exciting you once it’s totally allowed, the ‘forbidden’ thrill has faded—and that’s normal.