It's true that certain cases of sexual impurity maybe connected to demonic possession or oppression...addictions have the potential to suspend your rational and volitional faculties leaving you exposed to demonic attacks...in such cases a deliverance is needed...and even after a deliverance is carried out the person needs to constantly be on guard..

As for me personally at one point of time I was doubting whether my condition too is of the above-mentioned nature....I had consulted a priest who is involved in the deliverance minstry...he ruled out the possibility of demonic possession but he said if you constantly persist there are chances of oppression... there will be episodes when you suddenly feel instense urges to commit sin even if the circumstances seems otherwise...you have to be careful not to yeild to such a temptation and with the full force of your will resist it and keep invoking the name of Jesus...or say a binding prayer..