Blotchy Skin--Help!

Hi! I am getting married this August on a beach in Southern California. I am a little worried because whenever I get extremely nervous, my chest and neck get a little blotchy. My dress shows both areas. Does anyone have any advice as to what to do? Is there something I can take or put on my skin to prevent this from happening? Does anyone else have this same problem? Any advice would be great. Thanks! =o)