In my catalyst control center for my 3870x2 it says my memory clock speed is 901mhz and on newegg http://www.newegg.com/Product/Prod [...] 6814161224  
it says the 3870x2's memory clock speed is 1800mhz. Now my question is that, is there something wrong with my video card?  
(my core clock is the same as the video card on newegg 825mhz and by the way i have the sapphire version of the card)

it's normal! 2x 901 = 1800

but how come it isnt the same for the core clock?

Nothing wrong.  Memory is stated as effective memory which is actual memory x 2.  The core clock doesn't work the same as the memory, so in short nothing is wrong, don't worry about it.