if you are a psychic vampire [psi vampire] i'm not certain of all the signs, but a common one would be if you're tired, then suddenly hyper and the people around you are suddenly sluggish or yawning. psi vampires drain energy, not blood, so the effects can be seen in the living things around them. if this is the case you need to train this ability so you don't do it unknowingly. research psi vampires though, as i said, i don't know much about them.
blood sucking vampires are not real, you are human. you can look into sanguine, which is a vampiric lifestyle, but you are not a dracula, blood sucking, garlic hating vampire. that's pure fiction.