You might have inadvertently 'bump fired' it, meaning the trigger was allowed to bounce with recoil. Next time hold the trigger back when firing. The Garand has a similar issue and I actually had a couple double taps early on when I first bought it.
As for the sight picture, I'm having a hard time understanding your problem. Just press your cheek on the stock, raise up to eye level. Does it have the standard wood stock or something else?