I just tasted my mead after 3 months of brewing and now it tastes ok, but it is sparkling, like champagne. It also tastes a little like it. Actually, i never tasted mead before so i don't know hot it is, i just thought it would be smoother. Why did it happened? Is there something to help it?
That sparkle is carbon dioxide (CO2), one of yeast's main fermentation byproducts. It occurs in all fermentations (beer, wine, mead etc.) and residual amounts will linger in the beverage for many months after fermentation is done. Beer and champagne makers go to lengths to create and capture CO2 in solution for its characteristic sparkle, while wine makers often forcibly remove it by degassing, especially in wines that won't be aged long enough for it to dissipate on its own. For mead it depends entirely on how you want to serve it, with some preferring it still and others preferring it sparkling.
If you want to degas, here are a few existing questions on the subject:
That is from BJCG, Instructions to Mead Guidelines about carbonation
That is from BJCP STYLE GUIDELINES 2008 edition
A mead may be still, petillant, or sparkling. Still meads do not have to be totally flat; they can have some very light bubbles. Petillant meads are “lightly sparkling” and can have a moderate, noticeable amount of carbonation.
Next version of BJCP STYLE GUIDELINES 2014 Draft, which should be released sometime this March (or this year) adds.
Minor differences from stated carbonation level should not be a heavily-penalized or disqualifying fault.
So, it's okay. I have made 3 standard size (5-gallon) and 8 small (1-gallon) of mead. Only traditional semisweet mead (both times) had light carbonation, but it didn't cause any issues with the mead itself.