Menu Structure

I added a new page to my Menu and when I clicked save my menu lost it’s structure. It was previously in three levels but now it will only save as a flat menu, which means there are too many top level headings to display on my website, so it shows nothing and makes my website unnavigable. (I have currently removed many of the pages so that at least any vistors have something to look at and a contact page. Any suggestions
http://www.gardaweddings.co