iPhone not syncing

My iphone will not sync. It starts to sync/back up but before it can sync anything on my phone the "My IPhone" page on iTunes disappears. i have tried restarting both my phone and laptop, updated both of them as well. I tried different cords even though it still shows its charging on my phone even though I can't see its connected on my itunes (The page and icon just disappears on iTunes). I'm not sure what else to do? Thanks