Custom Menu Help!

Hello,

I made a custom menu off wordpress panel under appearances. I used to be able to add a page to the menu and then add a sub menu with other pages below that. However, now when I save the menu it automatically switches back to all the pages on the menu bar without any submenus. This is for the main menu.

I want it to be like this:
Hello (Main)
How to? (drop down)
Welcome (drop down)

Every time I save the menu it goes like this:
Hello (Main)
How to? (Main)
Welcome (Main)