Can i wear a Mouth Guard as a retainer..?

I am sorry to say that a mouth guard would not double as a retainer. Although you have the one that molds to your teeth, a retainer is pretty much an exact copy of the outside your teeth and can therefore hold them in so your teeth do not move. Save up as soon and as fast as you can because my cousin stopped wearing her retainer and she had to get braces on again. Good luck!