Are you sure you didn't accidentally put 2 blades in your cutter? That's what happens when you have more than one blade in the cutter, and it's very easy to make that mistake.
Also, be sure your rotary cutter has no lint build-up - and put a tiny dot of sewing machine oil on the blade. Run the cutter over a scrap before using it on 'good' fabric so be sure the oil isn't 'leaking'.