I don't think you are becoming ...possessed.. quite honestly, I have felt the same thing, but I find it is deep depression or I am dissociating... possibly this is what Is happening to you?

If you have chosen, for whatever reason not to have a therapist, have you asked your primary care doctor about medicine to help depression? It won't help the dissociation, but does help with depression. I take Viibryd and Welbutrin along with Klonopin when I have a serious anxiety attack (I don't take it as often as I use to)... I hate being on meds, but for now, as I come to terms with why I dissociate and feel the darkness at times, it helps me to cope and deal with what has haunted me my whole life so I can face the future with hope and no longer look back with dread.

Please know I don't think you are possessed, nor do I think there are demons, but I do believe at times the darkness and dissociation can make you feel that way. Sometimes we put off our own negative energy, when we try and suppress and hide from our past.. many times we don't even know we are doing it.

I do know that my horses have such a powerful positive energy that when I am around them, even for a short time, I feel so much more positive.. it is one of the few times I actually feel free and at total peace when I am with them. Animals are loving and very therapeutic. Do you have any animals that help you to feel safe and calm?

Hang in there... life is good and worth living.....