Phooey on those reversible blades, or ergonomic, or pricey left handed, etc. rotary cutters.
Try the "original" OLFA cutter
http://www.olfa.com/RotaryCuttersList.aspx?C=20 It is either left or right depending on which hand you use ...just turn it over so the blade is closest to the ruler edge. ( The 45mm is a good all-purpose size to begin with.)
YOU CAN DO THIS!!!!! Good luck.