how to remove this spell?

astrally speaking they are real. but physically they are not. no spell can change you into one. you're probably experiencing a placebo effect, where your mind thinks you're sick when you're not. very common, the brains too smart for it's own good lol. a study was done with placebos, people who even knew they were taking sugar pills began to feel better.

anyway, even if it was possible to become a vampire with a spell, you shouldn't of cast a vampire spell for better grades. if you wanted to use a spell, a study aid would work, maybe a spell to motivate you to work out. these would not instantly improve you, but they would help you remember more, and strengthen your muscles to run faster. you should always weigh your options before casting spells, a lot of the times they're not needed.