Snowboard size question?

so i have a brand new 2010 snowboard deck that i won at camp over summer (summer snowboard camp in oregon) and it's a little too big for me. i usually just cruise, go on small jumps and cruise in halfpipes. btw I am 14 years old, I weigh 130 pounds, I am 5' 4', I wear a size 8.5 to a size 9.0 boot, and my board is a size 156. I usually ride a size between 145 and 150 for park, but I just need to know about cruising. thanks for reading this question for so long and thanks for the help in advanced