I have the feeling like a ghost or spirit is in my body especially through my abdomen and lower back. is there a specific cause for this?

Unknown: The feeling of "having a ghost" in your body is difficult to diagnose, especially over the computer. I would see a dr. And let then take a good history and physcial to properly diagnose your condition, or at the least discuss your feelings in more detail.

If you live in an : area /house with an ghost, then yes if you think you have been possessed. Otherwise, its just an odd sensation, is there another way to describe it, and if so are you having problems that you need to see a urinary doctor/gynecologist or back doctor for spinal issues. rule out the medical issues first before you consider the supernatural ones.