OK...
1. Mirror up mode, As said it requires 2 shutter presses to cancel. The mirror up mode button is the second one down from the top to the left of the LCD screen. Check that it is not on
2. Live View. The live view button appears to be near the top of the right side of the rear LCD screen. When you are in live view, the eye piece is black and the picture on the rear LCD will move as you move the camera.
Check these first. It is possible you are pressing those buttons without knowing it, especially if you press the camera firmly into your face when you look thru the eyepiece. Don't ask how I know
Do you have a user manual? If not download one. They can be confusing but are very helpful