Hello JaneLee. You have given very little information to go on in order to help you. However, If you are genuinely born again of the Spirit of God you cannot be possessed by any demon. Once Jesus Christ enters into the heart of a person, once they are born again of the Spirit of God no demon can remain there. If there was indeed a demon there to start with.
Once Jesus Christ, who is the light, enters the dark heart the darkness cannot remain there any longer since light and darkness cannot share the same space. Light always pushes the darkness out just like in a dark room when the light is put on it pushes the darkness out.
Please provide more information on what is taking place so that one can effectively minister to you from the Word of God.