Evry time i stop my levocitrizine, my allergies come back... will i have to take this forever :(?

Not necessarily: Seasonal allergies do not typically go away, unless you move to a very different environment (and then you may develop new allergies). An allergist can give you immunotherapy (allergy shots) which is the only existing therapy that has the potential for long term or even permanent relief from allergy symptoms. Otherwise you try to manage with antihistamines and nasal sprays.