What am I doing wrong with my Ollie?

http://www.youtube.com/watch?v=kndscBVf6pw There is a video of me trying to ollie, sometimes I can ollie great, usually I can ollie really high. But when I land I usually land with my feet misplaced and fall over. I have really big feet, 12 and a half foot size, should I get a bigger deck? Would that help? Especially with kickflips. I have also been skating for a month,