I might be wrong, but it sounds like a demon spirit trying to get out, if you are a Christian it may be hard for it to stay in you that's why you can feel it go through your body, because you have the Holy Spirit living in you.  You could go to Deliverace for that. If you are a Christian that's just trying to oppress you, not posses you, because when you are reborn in Christ, satan and his demons cannot posses you, just oppress you. You can check out those definitions at dictionary.com