How to Recover iPhone Lost Contacts,SMS after downgrade iOS 7 to iOS 6?

Last night,I have downgrade my iPhone 5 from iOS 7 to iOS 6,I think the iOS 7 Operating system is very uncomfortable to used for me.Moreover,the ios 7 itself has a lot of bugs, although it's designed, innovative, I still prefer to use ios 6, so I downgrade ios 6 to ios 7 version, but I downgrade my iphone 5 to ios 6, my all iPhone Contacts,,call list recording and text messages are lost, but also my important pictures, videos and Notes were gone.I want to know how to recover lost data from my iPhone 5 after downgrade to iOS6?

Thanks a lot!