Could it have been a Kundalini awakening? I suddenly became very psychic after some months of meditation over a decade ago now, and while I didn't experience anything near as scary or demonic as you, it was pretty frightening for a while and I experienced a lot of sleep paralysis. It sounds like you opened up to more energy that you could handle and most of it was very negative. It sounds like you've worked hard on ways to manage this and reclaim your power which is amazing!