I constantly feel like I'm being watched.

Well, I suppose for starters I'm a 19 year old male, caucasian, living in the United States. In the past I've delt with both anxiety and depression, and may have had problems with bi-polar disorder, but was never diagnosed. I went off my medication for depression because I found a best friend, and didn't feel suicidal anymore. I still feel alright, not necessarily happy, but not depressed anymore, and the anxiety is nearly non-existent. However, as of I'd say about 6 months to a year now I've been having other problems. I don't know how to best explain it, but I will try. I constantly feel like I'm being watched. I feel extremely paranoid. I also heard a voice I'm sure wasn't real about 3 months ago, and as of recently (as in the past 3-4 weeks) I've been seeing things out of the corner of my eye. Tonight, I saw a full manifestation of a figure I believe to be a work of fiction. My house may very well be haunted, I've seen one entity before, but nothing like this.