My Main Menu disappears after scrolling down

Hey there, I'm not an expert at any of this stuff so go easy on me. My website is: searchingforyourzen.com The main menu (black menu) is perfect and I like how it looks, but when you scroll down the page and then scroll back up again, the main menu disappears and gets hidden underneath my header right / logo menu. I don't want the main menu to move with the scrolling (like the header right menu) but I do want it to show up in it's correct place when I return to the top of the page. Thanks for any tips.