Should I Be Embarred About My ?

My friends tease me about my s being "too big". I honestly don't see it, but still. I wear a 36 C and I'm 15. They'll say something abut them, people will hear, and they'll nag me about it too. I know they don't mean it in a mean way but still. I wear jackets all the time to try to make them look smaller, but my grandma says I shouldn't be be ashamed of them, or something like that. But I'm really shy when I comes to these kinds of things. What should I do?