Do I really have a yeast infection?

My mom thinks that I do because of some discharge in my underwear. I'm 13 and I don't have my period yet. She thinks that I do, and so she bought me Monistat 3. I've heard so much about how it really hurts to put it in and I'm a really wimpy kid who hates getting the flu shot! I don't even know if it is a yeast infection though, because I heard that some people get discharge before getting their period. Do I really have a yeast infection and is Monistat 3 worth using? How can I make it hurt less? Also, I've never even put in a tampon so I have no idea how to use it! Sorry that it's kind of personal, but I really don't know what to do! Please don't make fun of me!