You're being watched by a shadow lurker, most of them are harmless, i talk to the ones around me. I'm not sure dreaming about being a vampire makes you a vampire, ive studied them when i had my actual awakening where my vampirism genetics blossomed, im a vampire.
Slender man stalks kids that he finds with good qualities that could very well prosper into proxies, those usually with vivid imaginations and arent afraid of much as a child. When you get into your teens if you haven't already been taken that is usually when he starts getting closer (if you've been stalked as a child) and you'll develop slender sickness due to him being around and closer. Telling you everything would be pointless if you know a lot already, I have pages upon pages of bookmarked websites to go through.
Also the liking blood and evil thoughts could be a psychological pleasure. Just something to look into..