I bought a 1200' roll off a guy on Ebay and it was listed as "7 strand" paracord,now it arrives and I was cutting a piece to use and I opened it up and it only has three white strands, am I missing something or does 7 strand paracord only have three strands for some reason?
And as a matter of fact that could be dangerous to someone who supposed it could support more weight then it really could.

I am familiar with 7 stranded cord.  After cutting you can see and count 7 strands inside.

Sounds like you got something other than what was advertised.  Don't count on the strenght unless you proof load it.  

Check Mil-C-5040 if you can.  

Different types of cord in that spec.

CLASS MINIMUM    
    TEST (LBS.)
   
TYPE 1    100
TYPE 1-A  100
TYPE II   375  
TYPE III  550
TYPE IV   coreless  750