Check to see if you are crossing your eyes by looking at some magic eye (3D stereograms) if the pictures pop out from the page you're fine. That's the way you need to gaze at the pages.
If they cave in then you are crossing your eyes. To correct this go with the x technique as suggested by mastermind. Practice expanding your vision by noticing what you can see on both sides while looking straight ahead. Alternatively print out 12 magic eye pictures and practice looking at them with a soft gaze till you get the knack of getting them to pop out of the page repeatedly. Notice how it feels and apply that to photoreading.
This site helps to explain the technique http://www.vision3d.com/3views.html
Bottom of the page are links to developing the parallel vision. A link for the cocktail wienie http://www.vision3d.com/fftext.html
Alex