Full-blown demonic possession is quite rare.
However, demonic oppression is quite common. Many of the everyday vices and psychological issues with which many of us are afflicted are caused by demonic oppression. An exorcist may be of use here, also.
Here's a read of Fr. Amorth's take on the New Rite of Exorcism. The New Rite of Exorcism is Ineffective Against the Evil One .
He doesn't think much of it.
Did you ever read "Hostage to the Devil"? It's not for those with very sensitive natures. Very scary.