Okay, so I just have to wait for the next Page Rank update. This December was the last time it happened, so I should expect the next one in March.
I think domain age is not the factor to increase your pr. I saw lot of sites out there that is quiet older than mine but their pr is low. It's the number and quality of backlinks that can increase pagerank on every site.
Is it not true though that if your domain is too young, such as only one month, that the Google spiders will ignore it and wait for it to age a bit?