Your print setup and properties needs configuration.
Look here:
MSDN blog: The "Every Other Page Is Blank" Feature[
^]
Further, make sure you have not kept designer too long without any reason. Just to check margins, put a solid line with a red color or so and you will get to see how you have designed the report. It would be easy to correct it this way.
Tip: Easiest way to find and fix is to put a TEMPORARY colored thick border for the report.